Current State of Diagnosis of Breast Diseases: Contribution of Medical Imaging Technologies

Abstract

Breast pathology is diagnosed in every fourth woman under the age of 30 and in 60% of older women. Accuracy of clinical examination in detecting benign and malignant tumors does not exceed 50–60%, sensitivity is 40–69%, and specificity is 88–95%. Digital mammography is the principle diagnostic method for breast pathology in women over 40 years of age. Ultrasound is now one of the most widespread and affordable imaging methods for diagnosis of breast pathology, early and differential diagnosis of breast masses, and guidance of minimally invasive modalities. US is more valuable for specification of cysts, fibroadenomas, lipomas, some malignant tumors, and duct ectasia. Both diagnostic methods would benefit from their combined use in the differential diagnosis of cysts, large benign soft tissue tumors, tumor-like masses, and malignant tumors. To assess the spread of the tumor, CT or MRI is strongly recommended. The risk of breast cancer increases with age. The basic concept of screening is the detection of the disease early enough to ensure optimistic prognosis and change of the “natural” clinical course. In female population, large-scale mammography screening can reduce mortality rate from breast cancer by 15–30%. The efficiency of mammography for screening has been tested in numerous randomized studies. In order to unify imaging findings description, a specialized BI-RADS lexicon was developed. Report categories in accordance with BI-RADS lexicon are presented. BI-RADS categories used in echography correspond to the categories used in other diagnostic procedures.

These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

1.1 Imaging Techniques in the Diagnosis of Breast Diseases

Diagnosis of breast diseases is one important problem of women’s health globally. Breast pathology is diagnosed in every fourth woman under the age of 30 and in 60% of older women; 50–95% of women suffer from diffuse fibrocystic breast disease (Rozhkova 1993; Radzinsky et al. 2016).

The issues of early detection of breast tumors remain relevant due to the high morbidity and mortality of the female population. Breast cancer takes one dominating malignancy in women around the world. According to the WHO, each year more than 1,300,000 new cases are detected globally. The incidence of cancer has also increased in the majority of countries in Europe and in the world over the past decades. In 2012, 1.67 million patients with breast cancer were registered worldwide. More than half of the breast cancer cases are registered in economically developed countries, where breast cancer occurs in 6% of the female population throughout life. Morbidity in the Russian Federation for the last 10 years is shown in Fig. 1.1 (Kaprin et al. 2017).

Fig. 1.1

The incidence of malignant breast tumors in Russia in 2006–2016. The number of patients is indicated per 100,000 of population

Over the past 10 years, the number of patients with malignant breast tumors (malignant tumors) in the Russian Federation has increased by 30%; the most dramatic growth (34%) was observed in women aged 19–39 years: 68,205 cases in 2016 (439 cases per 100,000 of population). In 2016, 642,720 women with breast cancer were registered in Russian oncologic dispensaries.

Despite the increasing incidence of the disease, there has been a significant increase in the 5-year survival rate in Russia for the last decade, which was 61.9% in 2016 (Fig. 1.2) (Kaprin et al. 2017).

Fig. 1.2

Percentage of patients with breast cancer followed-up for ≥5 years in Russian oncologic facilities

Breast cancer amounts to 25.2% of all malignant tumors in the structure of oncological morbidity. It is the leading cause of cancer mortality among women. This is the result of late detection and, consequently, advanced stage at the time of diagnosis (Kaprin et al. 2017).

One important prognostic criterion for cancer is the extent of the tumor spread at the time of detection. An objective assessment of the changes in primary tumor size and regional lymph nodes in the process of preoperative systemic therapy is an essential part of the treatment (Semiglazov 2001). Decisions on the duration of preoperative treatment, the type of surgery, and the need for additional treatment methods depend on it.

High rates of morbidity and mortality from breast cancer force the development of new approaches to diagnosis. Early differential diagnosis of benign and malignant processes and evaluation of the severity and extent of malignancy are among the most burning problems. Despite the apparent availability and simplicity of breast examination, the incidence of detection of advanced disease was about 40%. In 2016, 24.7% of breast cancer were diagnosed in the first stage, 45% in the second stage, 21.5% in the third stage, and 8.2% in the fourth stage of the disease (Kaprin et al. 2017). 29.6% of cases of breast cancer were detected in late stages (III–IV); this is the evidence of low attention to obvious disease.

Nine hundred cases of breast carcinoma in situ were detected in Russia in 2016, which corresponds to 1.3 (2015—2.6) of cases per 100 of all newly diagnosed cases of cancer according to Kaprin et al. (2017). Early detection of breast malignancies is a priority. In this regard, the issues of effective detection of breast cancer, especially in the preclinical stage, are urgent. Secondary cancer prevention, especially screening, involves tests aimed at earlier detection of the disease, i.e., before the onset of signs and symptoms, which makes patients apply for medical assistance. The value of early diagnosis is that early cancer stage is curable.

Over the last decade, the number of patients with breast cancer has increased by 76.7% in Russia (from 21.9 to 38.7%), primarily due to preventive mammography (Kaprin et al. 2017). Technical equipment of medical facilities provides opportunities for solving the problems of the so-called secondary prevention of breast cancer (screening) by means of preventive examination of asymptomatic women.

High efficacy of diagnosis of early breast cancer makes it possible to use a highly effective complex of treatment and perform breast-conserving operations in combination with optimized programs of radiation and chemical therapy.

Methods of Breast Cancer Diagnosis

• 1. Preoperative:

  Main:

  • (a) Noninvasive:

    • Clinical examination (medical history, examination, palpation)

    • X-ray mammography

    • Ultrasound mammography

  • (b) Invasive:

    • Stereotactic core needle biopsy with histological investigation of biopsy samples

    • US-guided FNA with cytological examination

    • Vacuum aspiration biopsy under ultrasound or X-ray control

    • Cytological evaluation of nipple discharge

    • Preoperative labeling of impalpable tumors by marking needles

  Supplementary (upon indication):

  • Ductography

  • MRI

  • CT

  • Scintigraphy

  • Others (electrical impedance tomography, radiothermometry, etc.)

• 2. Intraoperative:

  • Urgent histological investigation

  • X-ray study of removed breast sector

• 3. Postoperative:

  • Histological examination of a specimen

Asymmetry of breasts, areolas, and nipples and deformity and dimpling of the skin and nipple when the arm is raised are clinical manifestations of breast tumors. Palpation usually reveals dense immobile tumor with rough surface. Ulceration may be observed in advanced stages. The skin and areola above the tumor are thickened (Krause symptom). Skin shrinkage and dimpling over the tumor or a symptom of “peau d’orange” are possible. Many breast diseases and tumors (benign and malignant) in the initial stages are asymptomatic.

Accuracy of the clinical examination in detecting benign and malignant tumors does not exceed 50–60%, sensitivity is 40–69%, and specificity is 88–95% (Shevchenko 1997; Korzhenkova 2004) (Fig. 1.3). Palpation also often fails to detect regional lymph nodes affection. The rate of errors in detection of metastatic lymph nodes reaches 32–45.8%.

Fig. 1.3

(a–d) Visual inspection in patients with breast cancer

Imaging techniques, particularly X-ray and ultrasound mammography, are essential in the diagnosis of breast pathology.

Mammography is a technology of obtaining a negative photographic image of the breast that reflects the projected attenuation of the X-ray radiation from mammography device passing through various tissues. First X-ray images of the breast were produced on amputated breasts by A. Salomon in 1913. Primary tumor with spread to the axillary lymph nodes was visualized. To now, the mammography is recognized worldwide as one of the most valuable diagnostic methods for a wide range of diseases, including breast tumors. Digital mammography is the principle diagnostic method for breast pathology in women over 40 years of age.

Mammography represents a two-dimensional image of the breast, which permits assessment of the thickness, glandular tissue density, and specification of the location, shape, borders, and size of focal lesions (Fig. 1.4). As a rule, mammography is performed in frontal (craniocaudal) and oblique (mediolateral) projections. Two projections provide imaging of the whole breast, allowing to localize the pathological process and differentiate the palpable lesions from the areas with impaired architectonics. In some cases, additional lateral projection is used as a supplement, in order to clarify the lesion location.

Fig. 1.4

(a–h) X-ray mammography. Breast cancer

Single projection mammography may miss 11–25% of tumors. The study of the sensitivity of mammography demonstrated the highest sensitivity (84%) in patients with correct breast positioning. Alternatively, if the images fail to display the whole breast (33.2%), the sensitivity decreased to 66.3%.

Modern X-ray equipment provides high-quality examination, since it has an automatic exposure system located on the surface of the digital detector, which is designed to recognize the characteristics of the target organ and to optimize contrast level of an image. High-contrast images are obtained owing to implementation of molybdenum (tungsten) anode and molybdenum filter with lower radiation load of the soft radiation spectrum. Adequate breast compression provides almost uniform thickness for achieving sharp mammogram images. Selective compression gives opportunity to estimate the delineation, density of the tumor, and reveal stellate structures, calcifications with a size of 50 μm. The quality of mammography is the result not only of technical characteristics of the equipment but also of the strict adherence to the technique of examination.

Mammography has the following advantages:

• Detection of impalpable breast lesions

• High diagnostic value

• Possibility of invasive and noninvasive diagnostic procedures

• Objective documented data accessible for dynamic analysis

Disadvantages of mammography are the following:

• Ionizing radiation

• Low value in dense and irregular structure of the breast

• Discomfort during the procedure due to breast compression

A patient is indicated for mammography in the following cases:

• Age of 40–50 years (with an interval of 2 years for preventive purposes)

• Age above 50 years (annually)

• Clinical signs or suspicion for breast carcinoma in any age

It should also be noted that standard mammography still has “blind” zones. For example, it is difficult to assess the axillary lymph nodes and the posterior-lateral segments of the breast that extend beyond the anterior axillary line.

Mammography is standardized, does not require any special training (except for studies with contrast agents), and has no contraindications (except for studies with contrast agents).

Tyurin (2011) reported that 2,936,212 mammographic examinations were performed in Russian Federation in 2009. Among them, 2,472,237 were screening mammograms. The sensitivity of mammography in breast cancer was 50–93%. Impalpable carcinomas can be detected with mammography in 76–82% of cases. The specificity of digital mammography in the differential diagnosis of impalpable lesions is 97.2–99.0%, the overall accuracy—98%. According to Rozhkova (1993), palpable breast tumor can be negative with mammography in 3.5–6% of cases.

Numerous randomized studies carried out in the USA by Shapiro, 1966, in Scotland by Alexander, 1999; in Canada by Morrison and Miller, 1992; in Sweden by Tabar, 1999 Andersson, 1997, and Nystrom, 2002; and in Finland by Hakama, 1997, demonstrated that 30–40% reduction in mortality from breast cancer was achieved due to introduction of mammographic screening. Depending on the age, which determines the condition of breast glandular tissue, there is a variability in the specificity and sensitivity of various screening tests. Mammographic screening of women over 50 years contributes to early breast cancer detection. The sensitivity of mammography in invasive breast cancer is lower in women of 40–49 years of age. It is 75% as compared with 93% in women of 50 years and older. This is associated with a greater proportion of fast-growing, more aggressive tumors in young women, resulting in appearance of interval breast cancer between regular screenings. About 8% of them are palpable by the time of mammography. It is believed that the tumor is local without metastases, if its size by the time of detection is smaller than 5–7 mm. The malignant tumors up to 1 cm in size are detected in 10–20% of cases. In fertile women, some tumors can grow up to 20–30 mm, remaining undetectable by mammography on the background of dense glandular tissue. Therefore, the use of other diagnostic methods (e.g., clinical examination) without mammography is useless in terms of early breast cancer detection.

Soft tissues of the axillary regions are rarely examined with radiography. The latter is replaced with mandatory ultrasound of regional lymph nodes, which exhibits high diagnostic value.

In recent years, mammography has undergone significant changes due to the introduction of tomosynthesis, contrast X-ray mammography, and their combinations. Introduction of these techniques eliminates the disadvantages of traditional X-ray mammography. However, they are also not perfect due to time consumption, high radiation exposure, the necessity for monitoring the biochemical indicators (creatinine), and the invasiveness of contrast procedures. It should be noted that due to introduction of tomosynthesis and contrast mammography the digital mammography method became multiparametric. Stereotactic biopsy with mammography is feasible, and impalpable lesions could be labeled under mammography control.

Utilization of new technologies in mammography and the combination of possibilities of analogue, digital, and 3D mammography are advantageous and open new prospects in diagnostics of breast malignancies (Rozhkova et al. 2008).

Digital tomosynthesis of the breast is a modern technology that implies the opportunities of 3D mammography. The breast undergoes a series of low X-ray exposures at different angles with subsequent conversion of obtained data into a series of tomograms with the use of a flat panel detector and the X-ray tube rotation.

Tomosynthesis allows to obtain three-dimensional images of breasts, to analyze each section, excluding the images of overlying or underlying tissues. Tomosynthesis has the following advantages over traditional mammography: it allows to significantly improve the diagnosis quality; reduces the number of additional examinations and biopsies due to improved imaging; increases breast cancer detection in patients with dense structure of breast tissue, FBD prostheses, and implants; reduces the time of examination; and makes the examination more comfortable due to breast compression.

The use of tomosynthesis in X-ray diagnostics increases the impalpable cancer detection, improves the differential diagnostics of the diseases associated with the glandular tissue restructuring by 4%, improves diagnosis of diseases accompanied by calcification by 5%, eliminates the need for additional studies (target mammography, additional settings), reduces the number of invasive interventions due to hyperdiagnosis, and raises the possibility of conservative surgery.

However, tomosynthesis has a higher radiation exposure than standard digital X-ray mammography and, therefore, extended monitoring intervals. Unfortunately, this method, as well as X-ray mammography, is often not effective in patients with dense breast tissue.

Breast MRI (magnetic resonance imaging), also known as MR mammography, implies T1- and T2-weighted images; complete magnetic resonance mammography (MRM) provides tomograms of pulse sequences in various planes (axial, sagittal, coronary) without any radiation load. The method allows noninvasive characterization of breast structure, detection of abnormal masses, differential diagnosis between benign and malignant tumors, and evaluation of nearby organs.

MRI is based on the analysis of proton behavior in hydrogen atoms. MR signal, which is captured by the HF coils, is generated due to the magnetization caused by the motion of protons in the transverse plane. Alterations of magnetic field intensity on the body cross sections provide spatial information. MRI allows to evaluate breast structure, to detect pathological lesions, to characterize their structure and the degree of homogeneity and margins, to reveal capsule, to specify invasion to the surrounding structures, and to visualize nearby lymph nodes. Dynamic MRI is a multiparameter technique that allows to detect and interpret minimal changes in breast based on a number of variables, which include different image characteristics (contrast, signal-to-noise ratio, resolution, time interval) and other parameters. At the same time, two important technical requirements are imposed for breast MRI: the use of special coils and contrast agents. According to Tyurin (2011), MRI of the breast constitutes up to 0.2% of the total number of tomography examinations.

The decision on breast MRI should be taken individually, depending on the specific clinical situation. The MRI method is not acceptable as a screening test. It is recommended to women with high-risk of breast cancer with BRCA 1 and BRCA 2 genes mutations.

MRI of the breast is often recommended in the following cases:

• Suspicious tumor in young women with dense breast tissue structure or at a genetic risk of breast cancer

• For determination of the disease extent

• For differential diagnosis of benign and malignant tumors

• For differential diagnosis of recurrent tumors and scarring in breast after previous surgery and radiation therapy (e.g., scar cancer)

• For staging, including assessment of adjacent areas and regional lymph nodes

• During dynamic monitoring of breast after reconstructive operations

• For adjuvant chemotherapy monitoring

MRM does not require special preparation; its contraindications are similar to those for MRI and to the administration of contrast agents.

Examination of breast by MRM takes 30–60 min. It is performed with a special coil, in the supine position. Certain attempts to shorten the duration of the procedure have been made. However, they have not achieved real success yet. Currently MRM is most frequently used for the assessment of breast implants and for the detection of malignant tumors. Specific pulse sequences allow to visualize silicone and to detect implant damage with practically 100% accuracy. Previously, this technical capability was used to detect silicone leaks after percutaneous breast plasty with gel. However, due to abandonment of this procedure, this issue is no longer relevant. For the detection of malignant tumors, the study is performed exclusively with bolus injection of contrast agent.

MRI has the following advantages (Serebryakova et al. 2011):

• High resolution and contrast of breast tissue

• Multiparameter evaluation of the detected changes (not only the image itself but also the cell density, the contrast agent kinetics, and even, if necessary, metabolites by MR spectroscopy are assessed)

• Possibility of simultaneous evaluation of both mammary glands and multiparametric analysis of an unlimited number of lesions

• Possibility of obtaining images in any random plane without mechanical repositioning, absence of “blind” zones

• Operator-independent procedure

• Noninvasiveness

• Absence of radiation load

Utilization of contrast agents (gadolinium-containing paramagnetics) significantly increases the diagnostic capabilities of MRI and allows to obtain better temporal and spatial resolution, differentiate malignant and benign breast tumors, and detect carcinomas up to 3 mm in size. Evaluation of contrast agent accumulation by an abnormal lesion with maximum intensity projection (MIP) reconstructions provides information of the tumor vasculature. Additional information is obtained by the analysis of contrast kinetics on T1-weighted images, such as contrast wash-in, washout, and time-intensity curves (Figs. 1.5, 1.6, and 1.7).

Fig. 1.5

Breast cancer. MRI. (a) Т1WI. (b) MIP reconstruction. (c) TIRM (turbo inversion recovery magnitude). (d) Signal time-intensity curve

Fig. 1.6

Breast cancer. MRM. Т1WI. (a) MIP. Coronal plane. Contrast accumulation in the central aspects of the right breast, deformation of vessel pattern. (b) Axial lymph node

Fig. 1.7

Mammary fibroadenoma. MRM. Т1WI: (a, b) TIRM (turbo inversion recovery magnitude). (c) Signal time-intensity curve. (d) MIP reconstruction

Dynamic studies make it possible to reliably differentiate lesions from normal tissue and to effectively detect extent, multifocality, and multicentricity of breast cancer. Sensitivity of contrast-enhanced MRM in the diagnosis of breast tumors is 83–100%, specificity—29–97% (Serebryakova et al. 2015). Berg et al. (2009) noted high diagnostic value of MRM in the detection of multifocality of breast cancer. Sensitivity of MRI in the diagnosis of breast cancer after augmentation mammoplasty is also high and reaches 85.7% with specificity of 98.2% (Savello and Shumakova 2014). High costs of MRI equipment make it reasonable to use the technology only in complicated diagnostic cases (Haylenko et al. 2005).

MRI allows detecting 2.7 times more tumors than X-ray mammography. A combination of these two methods increases detection of malignancies by 20% (Korzhenkova et al. 2006). MRI improves the detection of not only invasive tumors but also preinvasive ones, such as ductal carcinoma in situ and precancerous lesions (atypical ductal hyperplasia).

X-ray computed mammography (CT) is a modern radiological technology (Fig. 1.8). However, the technology is not a screening modality for breast carcinoma either. It is due to significant radiation, high cost of examination, and low throughput. CT practically has no advantages in early recognition of breast carcinoma as compared to mammography. However, the method is of great importance in assessment of cancer invasion and is indicated to detect spreading of the tumor to retromammary space, metastases in lymph nodes, and remote metastases. The diagnostic value of CT in detection of breast cancer is 60–62%, sensitivity is 100%, and specificity is 84% (Haylenko et al. 2005).

Fig. 1.8

Computed mammography. Breast cancer

The sensitivity and specificity of CT mammography with intravenous contrast enhancement in the diagnosis of recurrent breast cancer are 97.4% and 98.4%, in the diagnosis of metastases in regional lymph nodes—91.6% and 91.4%, respectively.

Mammoscintigraphy is a method of functional diagnostics of breast pathology, which is based on the assessment of distribution of radiopharmaceuticals in breast tissues (Fig. 1.9). ^99mTc-MIBI, ^99mTc-tehnetril, ^99mTc-teoksim, ^99mTc-tetrofosmin, and others can be utilized for the examination. Mammoscintigraphy along with studying of the breast permits assessment of isotope distribution in other chest structures including axillary areas and other regions of possible metastases.

Fig. 1.9

Bone scintigraphy. (a–d) 500 mBq ^99мТс Pyrfotech

The technology can be performed in two varieties: with gamma chamber (planar scanning, emission gamma tomography) or positron-emission tomography. In those cases, it can be carried out as an isolated breast scintigraphy, a polypositional scintigraphy of the chest, or as a single-photon emission computed tomography of the breast area and thorax.

The overall sensitivity of breast scintigraphy in the diagnosis of breast diseases is 72.4%; in fibrocystic breast disease, fibrous adenoma, and duct ectasia, 52.5%; in glandular, mixed FBD with palpable masses, 79.9%.

Mammoscintigraphy with ^99mTc-MIBI is not of great value in revealing primary breast carcinoma. Its sensitivity depends on the size of the lesion. The sensitivity differs in different cancer stages: at T1a (up to 0.5 cm), 26%; at T1b (up to 1 cm), 56%; at T1c (up to 2 cm), 95%; and at T2, 97%. The sensitivity of breast scintigraphy with ^99mTc-technetryl in primary breast tumor is 62–96.7%, specificity 71–100% (Kharchenko and Rozhkova 2005). At the same time, ¹⁹⁹Tl is slightly less sensitive than ^99mTc-MIBI the detection of regional lymph nodes metastasis.

SPECT with ¹⁹⁹Tl has a higher specificity (96.7%) compared to ^99mTc-MIBI (90%). SPECT with ¹⁹⁹Tl and ^99mTc-MIBI have higher sensitivity (98 and 98.5%, respectively) in detection of malignant breast tumors over 1 cm in size.

The sensitivity of scintigraphy in the detection of metastases of breast carcinoma in axillary lymph nodes is 51–85%, specificity is 91–93%, and diagnostic accuracy is 76–93% (Svensson et al. 2000).

In SPECT with ^99mTc-technetryl, the sensitivity, specificity, and overall accuracy in the diagnosis of axillary lymph nodes lesions were 75%, 84%, and 81%, respectively. In SPECT/CT these indicators increased to 75%, 89%, and 84%, respectively. In absence of pathological changes at SPECT/CT images, the probability of metastasis to sentinel axillary lymph nodes does not exceed 6%. The use of SPECT/CT along with the administration of 555 MBq Tm-99m-technetryl (MIBI) allows a more detailed evaluation of the infiltrative-edematous breast cancer. The use of the technique is appropriate at the final stage of the diagnostic program as a clarifying method.

Positron-emission tomography (PET) is the nuclear medicine technology based on utilization of various agents (monosaccharides, fat acids, antibodies, peptides, etc.), marked with positron emitting radionuclides. A modified gamma chamber is applied. It permits detection of gamma photons, which result from annihilation of positron with electron. Since gamma photons are emitted in opposite directions, it is possible to localize the place of their formation. Short-lived radioactive tracer isotope, which is chemically incorporated into a biologically active molecule (more often 18F-fluordeoxyglucose), allows to detect areas with increased metabolic activity that is often the characteristic of malignant cells.

PET is not widely applied in diagnosis of breast carcinoma now. Nevertheless, it is quite a promising technology. Indications for PET are limited due to low diagnostic value in small cancers, which are smaller than 1 cm in size. However, PET surpasses all known anatomic imaging methods in the localization of centers of breast carcinoma in soft tissues. Its possibilities should be applied for individualization of therapy and monitoring, since tumor metabolism decreases much faster than tumor size with effective treatment. Alternatively, absence of changes in tumor metabolism after treatment predicts its inefficiency.

Some studies of preoperative staging of breast cancer have shown that the sensitivity of PET in the diagnosis of multifocal lesion was twice higher than the sensitivity of combined mammography and US. Sensitivity and specificity of PET in metastatic lesions of axillary lymph nodes are 79% and 92%, respectively.

Development of PET for the diagnosis of breast cancer has the following main trends: technological improvements (development of more efficient detectors, hybrid systems, hardware and software implementation), search for new radiopharmaceuticals for the diagnosis of specific tumors, and prediction of effects of chemo-, hormono- and radiotherapy.

Combined methods (hybrid PET technologies) are quite in demand in modern medicine. They allow simultaneous imaging of morphological and metabolic changes, thus increasing the accuracy of tumor specification, and assessment of the disease extent beyond the primary lesion (Fig. 1.10).

Fig. 1.10

(a, b) PET/CT. Distant metastases of breast cancer in bones and spine

Currently, devices that combine PET with computed tomography and/or MRI (PET/CT, PET/MRI) are most common. Previously, PET and CT were regarded as complementary methods that were used consequently in the diagnosis of breast diseases. Combination of metabolic PET images and anatomical CT images required specific software. This problem was solved through the introduction of combined PET/CT. The first experimental scanner was created by Nutt and Townsend in 1998. Currently PET/CT is very important for detection of local recurrence of breast cancer, as well as regional and distant metastases.

PET/MRI is a recent achievement of hybrid radiology, and therefore this technology is still under study. According to the creators, this combined technology may be more sensitive in the diagnosis of some cancers and metastases than PET/CT. A great advantage of PET/MRI is significantly reduced radiation load in comparison with PET/CT and high contrast of soft tissues for MRI.

The importance of some other diagnostic methods for breast study (radiothermometry, electrical impedance computed tomography, laser mammography, microwave spectroscopy) is insignificant. Those technologies are rare and have limited clinical indications.

Electrical impedance tomography is a method of scanning of electrical impedance (full resistance) of breast tissues (Korzhenevsky 2003). It permits visual assessment of breast structure for differential diagnosis of various physiological conditions and changes, which accompany breast cancer. It analyzes distribution of electrical conductivity of breast tissues in several cross sections and detects pathological focus with abnormal value of electrical conductivity (Fig. 1.11).

Fig. 1.11

Electrical impedance tomography. (a) Normal breast. (b) Breast carcinoma

According to Trohanova (2010), electrical impedance mammography is a simple and efficient method of screening of focal breast pathology in women of different ages. The sensitivity, specificity, and positive and negative prognostic values account for the following figures: for cysts, 91%, 99%, 93%, and 99%; for diffuse cystic breast disease, 98%, 97%, 95%, and 99%; and for breast carcinoma, 92%, 98%, 92%, and 98% (Trohanova 2010).

Radiothermometry is a modality, which permits noninvasive measurement of the temperature in deep tissues. It is based on remote registration of infrared radiation by means of special devices. The results of the examination are presented as a thermogram (temperature plot). The areas with increased temperature are suspicious for breast malignancy due to higher metabolism and good vascularity. The character of breast thermograms depends on the age. Besides, there are individual features of location of “cold” and “hot” areas that sometimes complicate correct interpretation of the results. Radiothermometry is not often used nowadays in diagnosis of breast cancer because of a large number of false-positive tests, which can exceed 25%. The specificity of radiothermometry in diagnosis of breast carcinoma is reported 85%, sensitivity 84%, and in combination with US 91% (Yemelyanov et al. 2011).

Evidence-based medicine forces to perform the most significant diagnostic tests to work out the strategy of treatment. It seeks to obtain the data about tumor morphology. The conclusion about tumor structure results from invasive diagnostic procedures.

Core needle biopsy of breast tumors implies a stereotactic X-ray device and special instruments—biopsy gun- and guillotine-type needles. The technique is intended for an accurate collection of biopsy material for pathologic study and is a definite procedure in the diagnosis of breast lesions (refer to Chap. 12). The sensitivity of stereotactic biopsy in breast cancer is 97.6%, specificity is 100%, and diagnostic accuracy is 98% (Kuplevatskaya 2004).

Vacuum-assisted breast biopsy with stereotactic mammography or ultrasound guidance is an ergonomic and highly effective method of obtaining cellular material for verification (refer to Chap. 12). It permits to obtain multiple samples of tissue via a single needle. The procedure can be carried out not only with diagnostic but also with the treating purpose.

Wide application of US as a navigation method permits targeted fine needle aspiration biopsy (FNAB), which is highly efficient in obtaining samples from pathological foci (refer to Chap. 12). Subsequent cytology allows to define cellular structures in the sample and to differentiate lesions of various natures. According to Sinyukova et al. (2007), US-guided FNAB of breast lesions in combination with mammography and routine breast US improves early detection of breast cancer (up to 95–98%).

Ultrasound (US) is now one of the most widespread and affordable imaging methods for diagnosis of breast pathology, early and differential diagnosis of breast masses, and guidance of minimally invasive modalities. High efficiency of US in breast cancer diagnosis is provided by high sensitivity and specificity (Table 1.1).

Table 1.1 Diagnostic value of ultrasound in the diagnosis of breast cancer

The sensitivity of US in diagnosis of different variants of breast carcinoma depends on the histological type of a neoplasm. If added to mammography, US increases the sensitivity in detection of early impalpable cancer.

Significant development of US equipment allows detecting minimal pathological changes of breast parenchyma (lesions from 1 to 2 mm) and registering pathognomonic signs for differentiation between benign and malignant processes. Modern US scanners in the majority of cases permit confirmation of mammographic conclusion of a breast carcinoma and allow to diagnose X-ray-negative tumors. According to Otto (1993), the rate of detection of mammography-negative breast malignancies reaches 62%.

US provides high accuracy of breast cancer diagnosis, including impalpable and X-ray negative neoplasms, in the cases with previous mammography. The role of US in evaluation of surrounding structures, especially regional lymph nodes, is also important (Table 1.2).

Table 1.2 Diagnostic value of multiparametric ultrasound examination in the diagnosis of axillary lymph node metastases in breast cancer

Advanced ultrasound technologies, such as color-coded modes, three-dimensional image reconstruction, multiplanar scanning, ultrasound elastography, and contrast-enhanced echography, provide new diagnostic solutions and advantages.

Improvement of diagnostic equipment and accessibility of modern mammography and ultrasound are urgent issues for differential diagnosis of benign and malignant breast tumors with similar or equivocal clinical or imaging data. Mammography is preferable in changes in the gland tissues, such as local fibrosis, microcalcifications, or subcentimetric tumors. US is more valuable for specification of cysts, fibroadenomas, lipomas, some malignant tumors, and duct ectasia (Table 1.3). In the diagnosis of tumors, breast US is more competitive than X-ray mammography. Both diagnostic methods would benefit from their combined use in the differential diagnosis of cysts, large benign soft tissue tumors, tumor-like masses, and malignant tumors (Sencha 2015; Evseeva 2015). To assess the spread of the tumor, CT or MRI is strongly recommended.

Table 1.3 Comparison of the diagnostic value of different techniques for benign and malignant breast diseases

An effective breast examination flow integrates several imaging methods. This allows to increase the rate of detection of carcinomas at stage I from 13 to 80%. Information technologies that bring any specialty to a new level are actively integrated into mammology. A number of digital information technologies have been developed, such as CAD, computer-aided diagnostic system for screening; AWP, automated workplace of a radiologist-mammologist; radiology information system “IntegRIS”; and further on. These tools allow remote image reading and electronic archiving.

A system for integrated use of noninvasive and invasive diagnostic methods facilitates accurate timely diagnosis of breast diseases followed with individual management. The logistics of diagnostics and further tactics are demonstrated in Fig. 1.12).

Fig. 1.12

Flowchart of breast examination in outpatients

Complex examination includes detection, differential diagnosis of diffuse and focal breast changes, and further selection of management tactics. In the case of suspected cancer, this should comprise a puncture with morphological verification, surgical treatment, and effective monitoring.

1.2 Breast Cancer Screening

The risk of breast cancer increases with age. For a newborn girl, the risk of breast cancer is 3.5%, and the risk of dying from it is 1.8% (Korzhenkova 2004). The risk of developing breast cancer within 10 years is 1:72 for women 40–49 years old, 1:36 for women 50–64 years old, and 1:29 for women over 70 (Korzhenkova 2004). Unfortunately, there is no real way to prevent breast cancer. However, if breast cancer is detected at the preclinical stage with a tumor smaller than 1 cm³, the probability of metastases is low and the majority patients can be cured. Therefore, practicing physicians should focus on the detection of tumors 1 cm³ or smaller. According to some well-known model, the “natural history” of breast cancer lasts from the first hypothetical cancer cell till the death of the patient. The tumor reaches the size of 1 cm³ in 30 cell doublings, i.e., within the period of 2–18 years depending on the rate of tumor doubling. The growth and metastatic spreading rate determine the “natural history” of the disease.

Populational health check-ups aimed at early detection of the disease is actually a screening program. The goal of the oncologic screening programs is an active detection of asymptomatic and early stages of cancer. Such programs should be implemented with regard to their reasonability for those cancer types that represent an important public health problem at the country or regional level because of high morbidity and mortality rate.

The screening program (for breast cancer, as well as for cancer of other organs) should meet the following requirements:

• Meet theoretical basis of screening studies

• Include a variety of tests of high sensitivity, specificity, and diagnostic accuracy

• To be noninvasive, if possible minimally (or absolutely) harmless

• Equipment should be accessible and easy to operate and maintain

• Affordable and cost-effective

The basic concept of screening is the detection of the disease early enough to ensure optimistic prognosis and change of the “natural” clinical course. Two parameters are essential in assessing the screening test quality: sensitivity and specificity. High specificity tests are more important for healthy population. They provide a minimum number of false-positive results thus allow to avoid unnecessary biopsies and sometimes excessive surgical treatment. The probability of breast cancer detection with screening depends on the length of time period when the tumor is detectable preclinically. The longer this interval, the greater the chance of tumor detection. The effect of applying better treatment methods, noted along with the introduction of screening programs, should not be confused with the role and impact of screening on morbidity and mortality in particular cancer types.

Breast cancer screening includes a massive preventive examination of healthy women to identify early-stage tumors. The value of any breast cancer screening method is a possibility to identify favorable in prognostic terms asymptomatic preinvasive and early invasive forms of the disease, which in most cases correspond to a tumor up to 1 cm in size.

Breast cancer screening methods:

• 1. Patient’s self-examination

• 2. Medical examination, palpation of the breast and regional lymph nodes

• 3. Mammography

• 4. US

• 5. MRI

• 6. Laboratory study of hemostasis, immune and endocrine tests

About 80% of cases of breast cancer are self-detected, 10% detected by medical examination, and only 10% detected by mammography (Korzhenkova 2004).

Despite numerous publications on the importance of self-examination of mammary glands, its accuracy is not established. The sensitivity of the technique is about 26%, which is significantly less than in clinical examination and mammography. The decrease of sensitivity from 41% in women aged 35–39 to 21% among patients aged 60–74 years was observed. By now, there is no evidence of decrease in breast cancer mortality rate in self-examination group. According to various authors, the sensitivity of clinical breast examination is 40–69%, specificity—88–95%.

The main method of breast cancer screening is mammography. This method was a breakthrough in mammology as it was the first to supply an image of the breast structure and to detect impalpable neoplasms in a prompt and precise manner. Massive X-ray screening of healthy women for early breast cancer was proposed for the first time by Gohen in 1956 and was introduced into clinical practice by Frame and Carlson in 1975. Mammographic screening that is capable to detect a wide range of breast neoplasms is a typical example of successfully applied screening program in a number of European countries. The coverage of mammography screening in the USA was 70% in 2014. The highest coverage is reported by Scandinavian countries: in Finland, 90%, and in Sweden, 85%.

Tumor size is an important criterion for evaluation of the screening quality. The tumor of 0.5–1.0 cm in size is very difficult to detect clinically (Korzhenkova 2004). Mammography remains the best screening method for women with a “standard” risk of breast cancer (Semiglazov 2001). The efficiency of screening mammography is 77% in women 40–49 years of age and 95% in women over 50 years (Rasskazova and Rozhkova 2014). This is associated with two factors. First, in women under 50 years, fast-growing, aggressive neoplasms represent most cancer cases. In this group, the incidence of interval breast cancer is significantly higher. Second, the structure of breast tissue in fertile women makes it difficult to detect small malignant tumors. Positive screening tests indicate further examination (diagnostic mammography, US) in 2–22% of cases; diagnostic mammograms indicate biopsy in 12–78% (Korzhenkova 2004). Mammographic screening can reduce mortality from breast cancer by 30% in 5–7 years from the first screening and by 20% in 15–20 years from the first screening (Semiglazov 2001).

Efficiency of preventive mammography examination depends on the factors mentioned below:

• Standards compliance

• The quality of mammography equipment

• Qualification of the personnel

• Experience in conducting massive examinations

In order to conduct an effective screening, there is a need for trained personnel at mammography facilities to properly assess the inevitable (in 4–12% of cases) X-ray-negative breast tumors, as well as interval tumors, detected (in 15–25% of cases) in the intervals between cancer screening examinations (Semiglazov 2001).

The sensitivity of mammography is 77–95% with the specificity of 94–97%. It depends on the woman’s age, breast density, the quality of examination, etc. In women with dense mammary glands (young age, hormone replacement therapy), with low quality of mammography, or insufficient radiologist’s skills the diagnostic value of mammography may be low. Early detection of breast cancer reduced the mortality rate in women of 50–69 years to one-third.

However, mammography as a screening method has a number of drawbacks:

• “Interval” breast cancer occurs in 15–25% of cases; this is not the drawback of mammography itself but of screening programs in general.

• X-ray negative breast cancer occurs in 5–12% of cases. It is diagnosed with other methods.

• False-negative mammography results (5–25%).

Different countries use different intervals between screening mammography studies. It is, as a rule, 1–2 years, which are needed to reduce both costs and radiation exposure. Many authors report that interval cancer is usually detected at early stage and does not significantly affect the survival rate in this group of patients.

True X-ray-negative breast cancer occurs not so often (no more than in 12%). The majority of diagnostic mistakes are associated with high mammographic density of the mammary gland. The diagnostic accuracy of mammography in patients under 40 years is significantly lower than the same of US due to large glandular component. Alternatively, it is higher, as compared with US, in patients over 50 years with fatty involution of mammary glands.

A number of cases appear false negative at both mammography and clinical examination. This can result from a variety of factors, such as the quality of equipment, personnel’s skills, or breast anatomical features (e.g., density, scars). It leads to delayed diagnosis and late treatment. Some women refuse further examination and monitoring. Up to 25% of cases of invasive breast cancer are missed with mammography in patients aged 40–49 years, in comparison with 10% cases in patients aged 50–59 years. Therefore, it is necessary to use additional methods, possibly self-examination, MRI, or US in 40–49 year old women (Korzhenkova 2004).

Although MRI allows effective tumor detection in high-risk women with a mutation in the BRCA 1 or BRCA 2 gene, the MRI screening is unacceptable as a screening test due to high cost and lack of consistent standard approaches to its performance. MRI of the breast is less accessible for a patient. It is characterized by high sensitivity, but not specificity, thus producing a large number of false-positive results, which, in turn, can lead to unreasonable biopsy.

In daily practice of a mammologist-oncologist, US, as a rule, is not regarded as a breast cancer screening method. This is a consequence of the fact that US in outpatient facilities has limited value due to middle class equipment with low resolution and high dependence on the skills and experience of US specialist. However, in the last decade, advanced ultrasound equipment and new options (Doppler modes, 3D reconstruction, elastography, contrast enhancement, high-frequency probes up to 12–18 MHz) significantly expanded the diagnostic capabilities of US (Rybnikova et al. 2017). This method has a number of advantages that can compensate the drawbacks of mammography and make it appropriate for mass examinations in young female population. Echography is accessible and widely used, easy enough to perform, and effective in early and differential diagnosis of breast cancer and in assessment of surrounding tissues and regional lymph nodes (Sencha et al. 2017).

Differentiation of palpable breast cancer, diffuse fibrocystic breast disease, fibroadenoma, and lipoma is efficient with US screening. On the contrary, certain types of breast pathology, such as local fibrosis, adenosis, noninvasive breast cancer in situ, edematous-infiltrative, and some other types of breast cancer, are more effectively detected by X-ray method. US, in contrast to mammography, does not detect microcalcifications. Breast focal changes, which do not exclude malignant process, are detected with US and X-ray methods almost with the same rate. Diagnostic capabilities of US, mammography, and MRI are mostly determined by women’s age-specific features, necessitating complex use of these methods in breast pathology screening.

Laboratory screening of breast cancer selects patients of risk groups based on blood coagulation indicators and immune and endocrine tests (Adamyan et al. 1989). Various cancer markers (CA 15-3, CA 27-29, cancer embryonic antigen) are being used in modern oncology. At the same time, their use for screening is associated with significant expenses and technical limitations.

Since the sensitivity of mammography in the diagnosis of malignant tumors in dense breast is limited, it seems more efficient to use either a combination of mammography with US/MRI or just multiparametric mammography. It is especially valuable in patients with dense breast and/or scarring, for detection of metastatic lymph nodes, and in follow-up of high-risk patients. An effective examination system integrates mammography, US, MRI, and MDCT. This increases the detection of the stage I carcinomas from 13% to 80% (Semiglazov 2001).

The statistics on the detection of breast malignancies is different in patients of risk group (with familial or genetic risks of breast cancer) (Tables 1.4 and 1.5).

Table 1.4 Comparison of sensitivity of screening test for breast cancer in patients with family history of breast cancer

Table 1.5 Comparison of sensitivity of screening test for breast cancer in patients at high genetic risk of breast cancer

The sensitivity of mammography as a screening test in high-risk groups does not exceed 50%. However, additional use of the second screening method significantly increases its sensitivity. Nevertheless, WHO does not recommend using MRM and MDCT for screening purposes.

The population coverage is an important aspect for the success of screening program. In case of low turnout for routine screening (below 60%), its final effect will be minimal (Semiglazov 2001). The motivation of the population to undergo a screening test is based on permanent education and information through mass media, presentations, booklets, journal articles, and movies about the main risk factors of breast cancer development, methods of its detection, diagnosis, and treatment. High-quality mammographic screening finally results in significant (up to 30%) decrease in mortality rate. Women, who do not participate in mammographic screening for various reasons, should be aware that other methods (physical examination, self-examination) fail to reduce mortality rate from this disease.

In female population, large-scale mammography screening can reduce mortality rate from breast cancer by 15–30%. The efficiency of mammography for screening has been tested in numerous randomized studies in the USA, Scotland, Canada, Sweden, and Finland. The results have demonstrated significance of mammography, clinical breast examination, and self-examination.

Breast cancer screening, as a rule, consists of three stages:

• Stage 1. A city outpatient clinic, which supplies screening among the female population in assigned area, makes active calls and referrals for examinations. It also documents the screening results. Each outpatient clinic compiles lists of women aged 40–60 years, who live in the assigned area.

• Stage 2. A facility with mammograph equipment that performs the exams for the patients assigned to several different outpatient clinics.

• Stage 3. In case of pathological changes in mammograms, the patient is referred for the third screening stage to the district mammological department to specify the diagnosis. If cancer or benign mass is detected, the patient is referred for treatment to an oncological facility.

Early diagnosis of breast cancer contributes to reduction in treatment costs due to the following factors:

• Reduction of the volume of surgery from a mastectomy to a sector resection reduces the length of inhospital stay.

• Breast conserving treatment reduces the period of temporary disability and rehabilitation.

• There is no need for reconstructive surgery and prosthetic repair.

• In the absence of lymph node involvement, treatment can be curative without expensive chemotherapy (with a tumor up to 1 cm in diameter, T1a-1bN0M0).

The success of screening mammography is not limited with the reduction of mortality rate. It facilitates detection of neoplasms in early stages that results in less aggressive treatment and better cosmetic results. Mammographic screening initially leads to rapid increase in breast cancer incidence with subsequent decrease in the detection of common types of breast cancer in women, who undergo screening. Screening decreases the incidence of invasive breast cancer and mortality rate. According to WHO, a retrospective analysis of mortality trends following the development of screening programs for breast cancer in 30 European countries has demonstrated the following facts. During the period 1989–2006, breast cancer mortality rate decreased on the average by 19%, ranging from a 45% decrease in Iceland to a 17% increase in Romania. Different rates of mortality were noted in different age groups. In women under 50, the decrease was observed on average by 37% (ranging from 76 to 14%). In the age group of 50–69 years, the decrease was 21% (ranging from 40 to 14%). Average decrease in women of 70 years and older was only 2% (ranging from 42 to 80%). Continuing increase in mortality rates was registered in 17 countries concurrently.

The analysis of X-ray screening results in Finland in 1985–2004 has shown that screening activities contribute to the detection of 20% of new breast cancer cases. The neoplasms detected with screening were smaller. They were detected in earlier stages, with a 10-year survival rate of 90%, in comparison with 70% in the cases detected out of screening program (p = 0.003). A meta-analysis of seven randomized studies, which involved 500,000 women, who participated in mammography screening, demonstrated a 25% reduction in breast cancer mortality rate in the group of patients, who underwent screening. An in-depth analysis carried out by the experts group has revealed a 30–35% reduction in mortality rate in women aged 50–69 as a result of mammography screening. Mammography screening in Norway in 1996–2004 demonstrated a statistically insignificant 11% decrease in breast cancer mortality rate, while 40% of women underwent routine mammography examination before introduction of organized mammography screening.

The problem of the benefits and possible adverse aspects of breast cancer screening remains debatable. First of all, such doubts are associated with the problem of hyperdiagnosis, i.e., detection of breast cancer, which most likely will not be identified throughout the life span. The analysis of the results of 11 randomized screening programs conducted in the UK has shown that the problem of hyperdiagnosis really exists, but it is not possible to accurately estimate its significance. Rough calculations provide the following indicators: according to the forecast for women aged 50–52 subject to annual screening, 1% of the breast cancer hyperdiagnosis can be expected in the next 20 years. The analysis of the results of screening programs implemented in seven European countries has demonstrated that the percentage of hyperdiagnosis ranged from 10 to 20%.

Currently, it is recommended to inform all women about possible adverse aspects of mammographic screening, when they are invited for screening. The issue of favorable outcomes and possible risks of mammographic screening for women aged 40–49 years remains debatable. A meta-analysis of publications in MEDLINE for the period 1996–2005, as well as the data of the Cochrane Central Register of Controlled Trials, has been conducted. The analysis of the studies has shown a 7–23% reduction in breast cancer mortality rate in women from the age group of 40–49 years, who underwent mammographic screening. Screening with mammography is associated with an increased risk of mastectomy and a reduced risk of adjuvant chemotherapy and hormonal therapy. The risk of breast cancer mortality because of radiation exposure during mammography screening is very low and not comparable to the indicators of breast cancer mortality rate decrease due to early diagnosis. False-positive results have an insignificant impact on psychological state of women and their attitude to subsequent screening stages. Although many women complain of pain during mammography, few regard pain as a deterrent to subsequent examinations. According to the recommendations of US Preventive Services Task Force (USPSTF) of 2009, the mammography screening should be started in women from the age of 50 and should be conducted every other year. It is expected that in the future a comprehensive genetic study of breast tumors will make it possible to detect tumors with a potential for progress.

Taking into account the large number and a variety of specialists involved in diagnosis of breast pathology and screening examinations, it is important to introduce a unified terminology, which describes breast abnormalities. It should also be considered that during various diagnostic procedures, the breast is positioned in different aspects related to the body, and this can complicate anatomical description of the lesion localization.

In order to unify imaging findings description, a specialized BI-RADS lexicon was developed. Currently the fifth version of 2013 is in use (hereinafter freely available ACR version is given).

The structure of X-ray (mammographic) report includes:

• 1. Indications for examination

• 2. Description of the breast structure

• 3. Description of important findings according to the lexicon

• 4. Comparison with the previous tests (if available)

• 5. Assessment

• 6. Recommendations

• 1. Indication for Examination

  Provide a brief description of the indication for examination. This may be screening for an asymptomatic woman, recall of the finding detected by screening, evaluation of a clinical finding (specify the finding and its location), or follow-up of either a probably benign lesion or cancer treated with breast conservation. If an implant is present, both standard and implant-displaced views should be performed, and this should be stated in the mammography report.

• 2. Succinct Description of the Overall Breast Composition

  This is an overall assessment of the volume of attenuating tissues in the breast, which helps to indicate the relative possibility that a lesion could be obscured by normal tissue and that the sensitivity of examination thereby may be compromised by dense breast tissue. A few coalescent areas of dense tissue may be present in breasts with as little as 10% dense tissue, whereas primarily fatty areas may be present in breasts with as much as 90% dense tissue. Since mammography does not depict all breast cancers, clinical breast examination is a complementary element of screening. Findings at clinical breast examination should not be ignored and may have increased importance in the dense breast. The available data do not support the use of mammographic breast density for determining screening frequency. The following four categories of breast composition are defined by the visually estimated content of fibroglandular-density tissue within the breasts. Please note that the categories are listed as a, b, c, and d so as not to be confused with the numbered BI-RADS^® assessment categories. If breasts are not of apparently equal density, denser breast should be used to categorize breast density. The sensitivity of mammography for noncalcified lesions decreases as the BI-RADS^® breast density category increases. The denser the breast, the larger the lesion(s) that may be obscured. There is considerable intra- and interobserver variation in visually estimating breast density between any two adjacent density categories. Furthermore, there is only a minimal and insignificant difference in the sensitivity of mammography between the most dense breast in a lower-density category and the least dense breast in the next-higher-density category. These factors limit the clinical relevance of breast density categorization for the individual woman.

Breast composition category is estimated the following way:

• (a) The breasts are almost entirely fatty.

• (b) There are scattered areas of fibroglandular density.

• (c) The breasts are heterogeneously dense, which may obscure small masses.

• (d) The breasts are extremely dense, which lowers the sensitivity of mammography.

(a) The breasts are almost entirely fatty. Unless an area containing cancer is not included in the image field of the mammogram, mammography is highly sensitive in this setting (Fig. 1.13).

Fig. 1.13

(a, b) Mammography. The breasts are almost entirely fatty

(b) There are scattered areas of fibroglandular density (historically, there are scattered fibroglandular densities). It may be helpful to distinguish breasts in which there are a few scattered areas of fibroglandular-density tissue from those in which there are moderate scattered areas of fibroglandular-density tissue. Note that there has been a subtle change in the wording of this category, to conform to BI-RADS^® lexicon use of the term “density” to describe the degree of X-ray attenuation of breast tissue but not to represent discrete mammographic findings (Fig. 1.14).

Fig. 1.14

(a, b) Mammography. Scattered areas of fibroglandular density

(c) The breasts are heterogeneously dense, which may obscure small masses. It is not uncommon for some areas in such breasts to be relatively dense, while other areas are primarily fatty. When this occurs, it may be helpful to describe the location(s) of the denser tissue in a second sentence, so that the referring clinician is aware that these are the areas in which small noncalcified lesions may be obscured. Suggested wordings for the second sentence include: “The dense tissue is located anteriorly in both breasts, and the posterior portions are mostly fatty.” “Primarily dense tissue is located in the upper outer quadrants of both breasts; scattered areas of fibroglandular tissue are present in the remainder of the breasts” (Fig. 1.15).

Fig. 1.15

Mammography. The breast is heterogeneously dense, which may obscure small masses

(d) The breasts are extremely dense, which lowers the sensitivity of mammography. The sensitivity of mammography is lowest in this density category. The fourth edition of BI-RADS^®, unlike previous editions, indicated quartile ranges of percentage dense tissue (increments of 25% density) for each of the four density categories, with the expectation that the assignment of breast density would be distributed more evenly across categories than the historical distribution of 10% fatty, 40% scattered, 40% heterogeneously, and 10% extremely dense (Fig. 1.16). However, it has since been demonstrated in clinical practice that there has been essentially no change in this historical distribution across density categories, despite the 2003 guidance provided in the BI-RADS^® Atlas.

Fig. 1.16

(a, b) Mammography. The breast is extremely dense, which lowers the sensitivity of mammography

• 3. Clear description of any important findings

  It is assumed that most important findings are either of concern at screening, inherently suspicious, new, or seen to be larger/more extensive when compared to previous examination.

  • (a) Mass:

    • Size

    • Morphology (shape, margin)

    • Density

    • Associated calcifications

    • Associated features

    • Location

Margins and shape are estimated in accordance with Fig. 1.17.

Fig. 1.17

(a, b) Estimation pattern of the lesion shape and margins for description applying BI-RADS lexicon is used regardless of X-ray examination

Pathological lesion localization is described in accordance with Fig. 1.18 (applied to all imaging methods).

Fig. 1.18

(a) Segmentation of mammary gland regions to describe lesion localization. Used regardless of X-ray diagnostics method. Lateral projection (sagittal plane) and anteroposterior projection (axial plane). (b) Frontal projection

• (b) Calcifications:

  Morphology—describes typical benign type or describes shape of particles

  Distribution (may not be appropriate for typical benign calcifications)

  Associated features

  Location

  • Typical benign:

    • Skin calcifications.

    • Vascular calcifications.

    • Popcorn calcifications (involutional calcinated fibroadenomas).

    • Large (>1 mm) rod-shaped calcifications (sometimes may be branching) correspond to calcium deposition in dilated ducts.

    • Round calcifications, less than 1 mm in size, often multiple and grouped (deposits of calcium within acini).

    • Spherical, with clarification in the center, from 1 mm to 1 cm in size, with even, clear contours.

    • Ring-shaped or “egg shell” type.

    • “Milk of calcium” corresponds to deposits of calcium within cysts).

    • Calcifications within cutaneous scar (after surgical interference).

    • Dystrophic calcifications (usually after a trauma or radiation therapy). Generally of irregular shape, more than 0,5 mm in size.

  • Atypical calcifications: it is impossible to diagnose as unambiguously benign, usually small calcifications with vague or poorly identified contours that cannot be referred to a certain group.

  • Calcifications suspicious for malignant tumors:

    • Pleomorphic or granular, of various shapes and size, generally less than 0.5 mm in size

    • Small linear, punctate, or branching calcifications, in the form of a broken (or dotted) line less than 1 mm thick. Correspond to the filling of the affected ducts with calcium salts

• (c) Architectural Distortion:

  • Associated calcifications

  • Associated features

  • Location

• (d) Asymmetries (asymmetry, global asymmetry, focal asymmetry, developing asymmetry):

  • Associated calcifications

  • Associated features

  • Location

• (e) Intramammary lymph node (rarely important):

  • Location

• (f) Skin lesion (rarely important):

  • Location

• (g) Solitary dilated duct (rarely present):

  • Location

• 4. Assessment

  The incorporation of an assessment category in the overall summary of the mammography report is mandated by the Food and Drug Administration, Quality Mammography Standards, Final Rule. Whereas FDA-mandated assessments are not linked to management recommendations, BI-RADS^® assessment categories are designed to be concordant with specific management recommendations. The linking of assessment categories with concordant management recommendations further enhances sound medical practice.

  All final assessments (BI-RADS^® categories 1, 2, 3, 4, 5, and 6) should be based on thorough evaluation of the mammographic features of concern or after determination that an examination is negative or benign.

  An incomplete (category 0) assessment is usually given for screening examinations when additional imaging evaluation is recommended before it is appropriate to render a final assessment. There may be rare situations in the screening setting in which a category 4 or 5 assessment is used, but this practice is discouraged because it may compromise some aspects of outcome analysis. A recall (category 0) assessment should include specific suggestions for the next course of action (spot compression magnification views, US, etc.).

  Report categories in accordance with BI-RADS lexicon are presented in Table 1.6 (applied to all imaging methods).

Table 1.6 BI-RADS categories (applied to all imaging methods)

• (a) Mammographic Assessment Is Incomplete

Category 0: Incomplete—Need Additional Imaging Evaluation and/or Prior Mammograms for Comparison. For this assessment category, the text may be shortened to “Incomplete—Need Additional Imaging Evaluation” or “Incomplete—Need Prior Mammograms for Comparison,” as appropriate. There is a finding for which additional imaging evaluation is needed. This is almost always used in a screening situation. Under certain circumstances, this assessment category may be used in a diagnostic mammography report, such as when US equipment or personnel are not immediately available or when the patient is unable or unwilling to wait for completion of a full diagnostic examination. A recommendation for additional imaging evaluation includes the use of spot compression (with or without magnification), special mammographic views, and US. Category 0 should not be used for diagnostic breast imaging findings that warrant further evaluation with MRI. Rather, the interpreting physician should issue a final assessment in a report that is made before the MRI examination is performed.

In most circumstances and when feasible, if a mammography examination is not assessed as negative or benign, the current examination should be compared with prior examination(s). The interpreting physician should use judgment on how vigorously to attempt obtaining prior examinations, given the likelihood of success of such an endeavor and the likelihood that comparison will affect the final assessment. In this context, it is important to note that comparison with previous examination(s) may be irrelevant when a finding is inherently suspicious for malignancy. Category 0 should be used for prior image comparison only when such comparison is required to make a final assessment. When category 0 is used in the context of awaiting prior examinations for comparison, there should be in place a tracking procedure guaranteeing with 100% reliability that a final assessment will be made within 30 days (preferably sooner) even if prior examinations do not become available. Some mammography practices may reasonably choose never to use category 0 in the context of awaiting prior examinations simply because they do not have a 100% reliable tracking procedure. If a mammography examination is assessed as category 0 in the context of awaiting prior examinations and then the prior examinations do become available, an addendum to the initial mammography report should be issued, including a revised assessment. For auditing purposes, the revised assessment should replace the initial assessment (see the Follow-up and Outcome Monitoring section).

• (b) Mammographic Assessment Is Complete—Final Assessment Categories

Category 1: Negative. There is nothing to comment on. This is a normal examination.

Category 2: Benign. Like category 1, this is a normal assessment, but here the interpreter chooses to describe a benign finding in the mammography report. Involuting calcified fibroadenomas, skin calcifications, metallic foreign bodies (such as core biopsy and surgical clips), and fat-containing lesions (such as oil cysts, lipomas, galactoceles, and mixed-density hamartomas) all have characteristically benign appearances and may be described with confidence. The interpreter may also choose to describe intramammary lymph nodes, vascular calcification, implants, or architectural distortion clearly related to prior surgery while still concluding that there is no mammographic evidence of malignancy. On the other hand, the interpreter may choose not to describe such findings, in which case the examination should be assessed as negative (category 1). Note that both category 1 and category 2 assessments indicate that there is no mammographic evidence of malignancy. Both should be followed by the management recommendation for routine mammography screening. The difference is that category 2 should be used when describing one or more specific benign mammographic findings in the report, whereas category 1 should be used when no such findings are described (even if such findings are present).

Category 3: Probably Benign. A finding assessed using this category should have a ≤2% likelihood of malignancy but greater than the essentially 0% likelihood of malignancy of a characteristically benign finding. A probably benign finding is not expected to change over the suggested period of imaging surveillance, but the interpreting physician prefers to establish stability of the finding before recommending management limited to routine mammography screening. There are several prospective clinical studies demonstrating the safety and efficacy of periodic mammographic surveillance instead of biopsy for specific mammographic findings. Three specific findings are validated as being probably benign (noncalcified circumscribed solid mass, focal asymmetry, and solitary group of punctate calcifications). All the previously cited studies emphasize the need to conduct a complete diagnostic imaging evaluation before making a probably benign (category 3) assessment; hence, it is recommended not to render such an assessment in interpreting a screening mammography examination. The practice of rendering category 3 assessments directly from screening examination also has been shown to result in adverse outcomes: (1) unnecessary follow-up of many lesions that could have been promptly assessed as benign and (2) delayed diagnosis of a small number of cancers that otherwise may have been smaller in size and less likely to be advanced in stage. Also, all the previously cited studies exclude palpable lesions, so the use of a probably benign assessment for a palpable lesion is not supported by robust scientific data, although there are two single-institution studies that do report successful outcomes for palpable lesions. Finally, because evidence from previously cited studies indicates the need for biopsy rather than continued surveillance when a probably benign finding increases in size or extent, it is not prudent to render a category 3 assessment when a finding that otherwise meets “probably benign” imaging criteria is either new or has increased in size or extent. While the vast majority of probably benign findings are managed with an initial short-interval follow-up (6 months) examination followed by additional examinations until long-term (2- or 3-year) stability is demonstrated, there may be occasions in which a biopsy is done instead (patient preference or overriding clinical concern).

Category 4: Suspicious. This category is reserved for findings that do not have the classic appearance of malignancy but are sufficiently suspicious to justify a recommendation for biopsy. The ceiling for category 3 assessment is a 2% likelihood of malignancy, and the floor for category 5 assessment is 95%, so category 4 assessments cover the wide range of likelihood of malignancy in between. Thus, almost all recommendations for breast interventional procedures will come from assessments made using this category. By subdividing category 4 into 4A, 4B, and 4C, as recommended in Guidance chapter and using the cut points indicated therein, it is hoped that patients and referring clinicians will more readily make informed decisions on the ultimate course of action.

Category 5: Highly Suggestive of Malignancy. These assessments carry a very high probability (≥95%) of malignancy. This category initially was established to involve lesions for which 1-stage surgical treatment was considered without preliminary biopsy, in an era when preoperative wire localization was the primary breast interventional procedure. Nowadays, given the widespread acceptance of imaging-guided percutaneous biopsy, 1-stage surgery is rarely, if ever, performed. Rather, current oncologic management almost always involves tissue diagnosis of malignancy via percutaneous tissue sampling to facilitate treatment options, such as when sentinel node biopsy is included in surgical management or when neoadjuvant chemotherapy is administered prior to surgery. Therefore, the current rationale for using a category 5 assessment is to identify lesions for which any nonmalignant percutaneous tissue diagnosis is automatically considered discordant, resulting in the recommendation for repeat (usually surgical) biopsy.

Category 6: Known Biopsy-Proven Malignancy. This category is reserved for examinations performed after biopsy proof of malignancy (imaging performed after percutaneous biopsy but prior to complete surgical excision), in which there are nomammographic abnormalities other than the known cancer that might need additional evaluation.

BI-RADS terminology for MRM also differs from the terminology for mammography and US. The report of MRM results should have the following structure:

• 1. Indication for examination

• 2. MRI technique

• 3. Succinct description of the overall breast composition (screening only)

• 4. Clear description of any important findings

• 5. Comparison to previous tests

• 6. Composite reports

• 7. Assessment

• 8. Management

• 1. Indication for Examination

  Provide a brief description of the indication for examination. For example, this may be high-risk screening, follow-up of a probably benign lesion, follow-up of cancer treated with neoadjuvant chemotherapy, or evaluation of the newly diagnosed cancer patient. As background parenchymal enhancement can be affected by cyclical hormonal changes, it may be helpful to include menstrual history. If the patient is pre-menopausal, the week of the menstrual cycle may be important information to aid in interpretation. Current therapy (neoadjuvant, adjuvant, hormonal, or radiation therapy) for breast cancer treatment in the pre- or postsurgical setting may be important information and may inform exam interpretation. The indication for examination should contain a concise description of the patient’s clinical history, including:

  • (a) Reason for performing the exam (e.g., screening, staging, problem solving)

  • (b) Clinical abnormalities, including size, location, and duration:

    • Palpable finding

    • Nipple discharge

    • Other pertinent clinical findings or history

  • (c) Previous biopsies:

    • Biopsy type

    • Biopsy location

    • Benign or malignant pathology (cytology or histology)

  • (d) Hormonal status if applicable:

    • Pre- or postmenopausal

    • Menstrual cycle phase (second week or other) or last menstrual period

    • Peripartum

    • Exogenous hormone therapy, tamoxifen, aromatase inhibitors, or other hormones or medications/herbs/vitamins that might influence MRI

• 2. MRI Technique

  Give a detailed description of the technical factors of how the MRI examination was obtained. At a minimum, a bright-fluid sequence of both breasts should be obtained. Pre- and post-gadolinium T1-weighted images should be obtained, preferably with fat suppression, simultaneously of both breasts. Subtraction imaging may be desired as well as other as processing techniques and parametric analysis. Elements of this description routinely include:

  • (a) Right, left, or both breasts

  • (b) Location of markers and their significance (scar, nipple, palpable lesion, etc.)

  • (c) Weighting:

    • T1 weighted

    • T2 weighted

    • Fat saturation

    • Scan orientation and plane

    • Other pertinent pulse sequence features

  • (d) Contrast dose:

    • Name of contrast agent

    • Dosage (mmol/kg) and volume (in cc)

    • Injection type: bolus or infusion

    • Timing (relationship of bolus injection to scan start time and scan length)

    • If multiple scans: number of post contrast scans and acquisition techniques of each (how fast, how many slices, and slice thickness)

  • (e) Post-processing techniques as applicable:

    • MPR/MIP

    • Time/signal intensity curves

    • Subtraction

    • Other techniques

• 3. Succinct description of overall breast composition

  This should include an overall description of the breast composition, including:

  • (a) The amount of FGT that is present:

    Breast Tissue—Fibroglandular Tissue (FGT) (Figs. 1.19, 1.20, 1.21, and 1.22)

    • Almost entirely fat

    • Scattered fibroglandular tissue

    • Heterogeneous fibroglandular tissue

    • Extreme fibroglandular tissue

Fig. 1.19

Example of FGT assessment. Т1-weighted MR image in axial plane and Т2-weighted MR image with fat suppression in sagittal plane. Almost entirely fat

Fig. 1.20

Example of FGT assessment. Т1-weighted MR image in axial plane and Т2-weighted MR image with fat suppression in sagittal plane. Scattered fibroglandular tissue

Fig. 1.21

Example of FGT assessment. Т1-weighted MR image in axial plane and Т2-weighted MR image with fat suppression in sagittal plane. Heterogeneous fibroglandular tissue

Fig. 1.22

Example of FGT assessment. Т1-weighted MR image in axial plane and Т2-weighted MR image with fat suppression in sagittal plane. Extreme fibroglandular tissue

The four categories of breast composition are defined by the visually estimated content of FGT within the breasts. If the breasts are not of apparently equal amounts of FGT, the breast with the most FGT should be used to categorize breast composition. Although there may be considerable variation in visually estimating breast composition, categorizing based on percentages (and specifically into quartiles) is not recommended. We recognize that quantification of breast FGT volume on MRI may be feasible in the future, but we await publication of robust data before endorsing percentage recommendations. We urge the use of BI-RADS^® terminology instead of numbers to classify breast FGT in order to eliminate any possible confusion with the BI-RADS^® assessment categories, which are numbered.

• (b) The amount of background parenchymal enhancement in the image:

  Breast Tissue—Background Parenchymal Enhancement (BPE) (Fig. 1.23)

  • Minimal

  • Mild

  • Moderate

  • Marked

Fig. 1.23

Example of BPE assessment. Т1-weighted MR images with fat suppression and contrast enhancement. Axial plane. A minimal, B mild, C moderate, D marked

The four categories of BPE are defined by the visually estimated enhancement of the FGT of the breast(s). If the breasts are not of apparently equal amounts of BPE, the breast with the most BPE should be used to categorize BPE. In the event that treatment has altered BPE in one or both breasts, this can be reported. Although there may be considerable variation in visually estimating BPE, categorizing based on percentages (and specifically into quartiles) is not recommended. Quantification of BPE volume and intensity on MRI may be feasible in the future, but we await publication of robust data on that topic before endorsing percentage recommendations. We recognize that there are variations in BPE distribution and morphology. However, we defer on recommending descriptions of distribution or morphology until additional data are available. Currently, BPE refers to the volume of enhancement and the intensity of enhancement. For consistency, BPE should be included for all patients.

On bilateral scans, describe whether the pattern is asymmetric or symmetric, if appropriate. Asymmetric denotes more significant enhancement in one breast than in the other. Symmetric enhancement is mirror image.

• (c) Whether implants are present if an implant is present, it should be so stated in the report. Information should include its composition (saline, silicone, or others) and the number of lumens (single or multiple).

• 4. Clear description of any important findings

  Abnormal enhancement is unique and separate from BPE. Its description should indicate the breast in which the abnormal enhancement occurs, the lesion type, and modifiers. The clinical location of the abnormality as extrapolated from the MRI location (based on clock-face position and quadrant location) should be reported. It should be recognized that there may be variation in location of a clinically detected lesion (patient is upright or supine), a lesion detected by mammography (patient is upright and compressed), a lesion detected by sonography (patient is supine or supine oblique), and an MRI-detected lesion (patient is prone) based on positional differences. A more consistent measurement is the distance from the nipple. It is encouraged that distance from the nipple for a lesion be reported in order to facilitate correlation between modalities, although it should be understood that one should expect some difference in distance from the nipple among the breast imaging modalities. For bilateral axial examinations, the breasts should be pointing up, following the cross-sectional imaging convention. The descriptors should include:

  • (a) Size

  • (b) Location:

    • Right or left

    • Breast quadrant and clock-face position (or central, retroareolar, and axillary tail descriptors)

    • Distance from the nipple, skin, or chest wall in centimeters (if applicable)

Descriptors for abnormal enhancement:

• (c) Findings associated with abnormal enhancement include:

  • Artifacts that affect interpretation

  • Focus: a tiny dot of enhancement that does not clearly represent a space-occupying lesion or mass and does not clearly show a mass on precontrast imaging.

  • Masses: space-occupying lesions, usually spherical or ball-like, may displace or retract surrounding breast tissue. Descriptors—modifiers describing a mass:

    • Shape: describes the overall morphology of the enhancement:

      • Oval (includes lobulated)

      • Round

      • Irregular

    • Margin: describes the borders:

      • Circumscribed

      • Not circumscribed:

        • Irregular

        • Speculated

    • Internal enhancement characteristics:

      • Homogeneous

      • Heterogeneous

      • Rim enhancement

      • Dark internal septations

  • Non-mass enhancement (NME): modifiers describing enhancement patterns with a specific MRI pattern:

    • Distribution:

      • Focal

      • Linear

      • Segmental

      • Regional

      • Multiple regions

      • Diffuse

    • Internal enhancement patterns (for all other types):

      • Homogeneous

      • Heterogeneous

      • Clumped

      • Clustered ring

  • Intramammary lymph node (rarely important)

  • Skin lesion (rarely important)

  • Non-enhancing findings:

    • Ductal precontrast high signal on T1W

    • Cyst

    • Postoperative collections (hematoma/seroma)

    • Post-therapy skin thickening and trabecular thickening

    • Non-enhancing mass

    • Architectural distortion

    • Signal void from foreign bodies, clips, etc.

  • Associated features:

    • Nipple retraction

    • Nipple invasion

    • Skin retraction

    • Skin thickening

    • Skin invasion:

      • Direct invasion

      • Inflammatory cancer

    • Axillary adenopathy

    • Pectoralis muscle invasion

    • Chest wall invasion

    • Architectural distortion:

  • Fat-containing lesions

    • Lymph nodes:

      • Normal

      • Abnormal

    • Fat necrosis

    • Hamartoma

    • Postoperative seroma/hematoma with fat

  • Stability: describe how the enhancement changed (if new, stable, or changed in size from previous examination)

  • Kinetic curve assessment (if applicable):

    • The fastest enhancing portion of the lesion or the most suspicious washout curve pattern in the lesion should be assessed:

      • Sample fast enhancing areas

      • Sample for and report on the worst looking kinetic curve shape

    • Signal intensity/time curve:

      • Initial enhancement phase—describes the enhancement pattern within the first 2 min or when the curve starts to change:

        • Slow

        • Medium

        • Fast

      • Delayed phase—describes the enhancement pattern after 2 min or after the curve starts to change:

        • Persistent

        • Plateau

        • Washout

  • Implants:

    • Implant material and lumen type:

      • Saline

      • Silicone:

        • Intact

        • Ruptured

    • Other implant materials (such as soy oil, polypropylene, polyurethane, and sponges; includes direct injections)

    • Lumen type

    • Implant location:

      • Retroglandular

      • Retropectoral

    • Abnormal implant contour:

      • Focal bulge

    • Intracapsular silicone findings:

      • Radial folds

      • Subcapsular line

      • Keyhole sign (teardrop, noose)

      • Linguine sign

    • Extracapsular silicone:

      • Breast

      • Lymph nodes

    • Water droplets

    • Peri-implant fluid

Also, we recognize that other techniques may be used in the evaluation of breast lesions. Newer and evolving techniques are constantly being introduced. Findings from other techniques, such as diffusion-weighted imaging or MR spectroscopy, should be reported if clinically important.

• 5. Comparison to Previous Examination(s)

  Include a statement indicating that the current examination has been compared to previous examination(s) with specific date(s). If this is not included, it should be assumed that no comparison has been made; however, it is preferable to indicate explicitly that no comparison was made. Comparison to a previous examination may assume importance if the finding of concern requires an evaluation of change or stability. Comparison is less important when the finding has characteristically benign features. Comparison may be irrelevant if the finding is inherently suspicious for malignancy. Information in this area should include:

  • (a) Previous MRI—date of examination

  • (b) Other imaging studies (mammogram, US, nuclear medicine examination, others) and date of examination

• 6. Assessment

  This is a description of an overall summary of MRI findings, including assessment. Incorporating an assessment category in the overall summary of the breast MRI report is sound medical practice. All final impressions should be complete with each lesion fully categorized. An incomplete assessment (category 0) is used when full diagnostic imaging has not been performed and should be given only when additional imaging or clinical evaluation is recommended to establish the benignity of a finding (e.g., a possible intramammary lymph node or fat necrosis at MRI may require additional mammography and/or US examination). Interpretation is facilitated by recognizing that almost all MRI examinations may be classified into a few assessment categories, listed in the section on Assessment Categories.

• 7. Management

  This is a description of patient management recommendations, as appropriate. If an incomplete assessment (category 0) is rendered, a specific suggestion for the next course of action should be given (physical examination, diagnostic mammography, targeted diagnostic US, etc.). Note that an incomplete assessment (category 0) should not be rendered when recommending targeted US in order to determine the feasibility of performing biopsy using sonographic guidance; such a scenario requires the use of a category 4 or 5 assessment (suspicious or highly suggestive of malignancy). If a suspicious abnormality is detected, the report should indicate that a biopsy should be performed in the absence of clinical contraindication. This means that the radiologist has sufficient concern that a biopsy is warranted; the term “clinical contraindication” indicates that there may be reasons why the patient and her physician might wish to defer the biopsy.

• 1. Assessment is incomplete

Category 0: Incomplete—Need Additional Imaging Evaluation. Use this for a finding that needs additional imaging evaluation. This may be used for a technically unsatisfactory scan or when more information is needed to interpret the scan. A recommendation for additional imaging evaluation might involve a repeat MRI with satisfactory technique or obtaining information with other imaging modalities (mammographic views, US, etc.). The radiologist should use judgment in how vigorously to pursue previous studies.

Every effort should be made not to use category 0. The reason for this is that almost always there is enough information on the initial breast MRI examination to provide a management recommendation. In general, the decision to biopsy or not may be made on the basis of the existing MRI study. A situation in which a final assessment of 0 may be helpful is when a finding on MRI is suspicious, but demonstration that the finding is characteristically benign on an additional study would avert biopsy. For example, if a small mass is suspicious on MRI but there is a possibility that it may represent a benign finding, such as an intramammary lymph node, then a category 0 assessment may be made, with the recommendation for targeted US (that might demonstrate characteristically benign features) to possibly avert biopsy. Another example would be a suspicious finding at MRI that may represent fat necrosis, with the recommendation for diagnostic mammography (that might demonstrate characteristically benign features) to possibly avert biopsy. If a category 0 assessment is rendered at MRI, detailed recommendations should describe the subsequent diagnostic imaging workup and the level of suspicion (pertinent in case the additional imaging does not establish benignity). When additional studies are completed, a final assessment is rendered. If the additional studies are described in the same report, separate paragraphs indicating the pertinent findings from each imaging study will contribute to the final integrated assessment that takes all the findings into consideration.

• 2. Assessment is Complete—Final Assessment Categories

Category 1: Negative. There is nothing to comment on. This is a normal examination. No abnormal enhancement was found; routine follow-up is advised. There is nothing to comment on. The breasts are symmetric, and no enhancing masses, architectural distortion, or suspicious areas of enhancement are present. Category 1 includes a normal description of breast composition (amount of FGT) and the degree of BPE. It should be emphasized that BPE is a normal finding, and short-term follow-up is not necessary to assess BPE for stability.

Category 2: Benign. Like category 1, this is a normal assessment, but here the interpreter chooses to describe a benign finding in the breast MRI report. The interpreter may describe a benign finding such as intramammary lymph node, implants, metallic foreign bodies (such as core biopsy and surgical clips), enhancing and non-enhancing fibroadenomas, cysts, old non-enhancing scars or recent scars, postoperative collections, and fat-containing lesions (such as oil cysts, lipomas, galactoceles, and hamartomas). On the other hand, the interpreter may choose not to describe such findings, in which case the examination should be assessed as negative (category 1). Both category 1 and 2 assessments indicate that there is no evidence of malignancy. The difference is that category 2 should be used when describing one or more specific benign MRI findings in the report, whereas category 1 should be used when no such findings are described (even if such findings are present). The committee supports a directive for annual follow-up MRI and mammography after either a category 1 or 2 screening MRI assessment, in line with established guidelines for high-risk screening.

Category 3: Probably Benign. A finding assessed using this category should have a ≤2% likelihood of malignancy but greater than the essentially 0% likelihood of malignancy of a characteristically benign finding. A probably benign finding is not expected to change over the suggested period of imaging surveillance, but the interpreting physician prefers to establish stability of the finding before recommending management limited to routine breast screening. Although data are becoming available that shed light on the efficacy of short-interval follow-up for selected MRI findings, at the present time, such management recommendations are based on limited data. The use of a probably benign (category 3) assessment is reserved for specificfindings that are separate from the BPE and are very likely benign. The use of a category 3 assessment has been intuitive in the past; however, there are several studies that specifically address rates of malignancy and, to a very limited extent, types of lesions. Although these studies examined different populations of patients, several of them were able to demonstrate a ≤2% malignancy rate, demonstrating the feasibility of using category 3 assessments at MRI. However, none of the studies provided PPVs for specific types of lesions, so the use of category 3 assessment at MRI remains intuitive for radiologists who lack extensive (audited) personal experience with any given specific type of lesion. Currently, this is an evolving area that needs the support of robust data before an unqualified endorsement is made to use category 3 assessments at MRI.

As at mammography, if a probably benign finding is smaller or less prominent (i.e., less contrast enhancement) on follow-up examination, the finding should be assessed as benign (category 2), eliminating the need for continued surveillance imaging. When a finding that otherwise meets probably benign imaging criteria is either new or has increased in size, extent, or conspicuity, then a recommendation for biopsy would be prudent and a recommendation for follow-up should not be rendered. BPE, a benign finding on nearly all MRI examinations, should not be the reason for a probably benign assessment. However, if findings cannot be ascribed to normal variation of BPE and there is a question about whether observed enhancement could be transient and related to the hormonal status of the patient, then a probably benign (category 3) assessment with a recommendation to return for very-short-interval follow-up (2–3 months) may be appropriate. Because a benign hormonal enhancement can vary from cycle to cycle, a category 3 assessment may be used for the menstruating patient who was scanned in a suboptimal phase of her cycle; a follow-up MRI examination should be scheduled for the optimal (week 2) phase of her cycle. Additionally, a category 3 assessment may be used for the postmenopausal patient who is on hormone replacement therapy (HRT) and in whom probable hormonal enhancement is observed. Stopping HRT for several weeks and repeating the scan may be warranted in this scenario. It should be emphasized that unexplained areas of enhancement that are demonstrated to be due to HRT are uncommon. As with mammography, if the finding is smaller or less prominent (i.e., less contrast enhancement) at follow-up examination, the finding is benign. Recommendations will likely undergo future modifications as more data accrue regarding the validity of using category 3 assessments at MRI, the follow-up interval required, and the type of findings that should be followed.

Follow-Up of Foci

Foci are defined as small dots of enhancement that are unique and stand out from the BPE. They are too small to be accurately assessed with respect to margin or internal enhancement. Indeed, if margin or internal enhancement can be assessed, the finding should be considered a small mass and not a focus. New foci or foci that have increased in size should be viewed with suspicion and carefully evaluated. Correlation with bright-fluid imaging (T2W imaging or STIR imaging) can be helpful in the evaluation of a focus. If a correlate is uniformly very high in signal intensity or if cyst-like features are identified, the focus may be assessed as benign. (Most of these foci represent lymph nodes or small myxomatous fibroadenomas.) However, if the focus does not have a very high signal correlate on bright-fluid imaging, then the focus may or may not be benign. These foci may be followed or biopsied. In certain cases (if the finding is new or increased in size), the focus always should be biopsied. Note that malignant foci may be brighter than the surrounding FGT, although they do not usually appear cyst-like.

Follow-Up of Masses

Masses that enhance and are identified on an initial MRI examination should undergo assessment based on morphology and kinetics. It has been documented that occasionally malignancy may demonstrate benign-appearing MRI features, such as an oval or round shape with a circumscribed margin and homogeneous internal enhancement. Therefore, in a scenario in which the stability of the finding is unknown, periodic surveillance imaging may be appropriate, depending on various factors that affect the prior probability of malignancy (age, cancer risk, etc.) as well as the patient’s willingness to accept surveillance imaging as an alternative to biopsy, given less than robust data that support a watchful-waiting approach. If surveillance imaging is undertaken, an increase in size of the mass should prompt immediate biopsy.

Follow-Up of NME

NME that is unique and separate from the overall background enhancement should undergo assessment based on morphology and kinetics. Bright-fluid imaging sequences can be helpful in these instances to demonstrate any associated cysts, which may support a diagnosis of focal fibrocystic change and a benign (category 2) assessment. However, limited data on linear, clumped, and segmental enhancement indicate that these findings should not be followed, as the malignancy rate appears to be greater than 2%. 4 At this time, the literature is not sufficiently robust to endorse the use of a category 3 assessment for NME.

Timing of Follow-Up

Final assessment category 3 is best used for a unique focal finding and managed with an initial short-interval follow-up (6 months) examination followed by additional examinations until long-term (2- or 3-year) stability is demonstrated. For category 3 assessments, the initial short-term follow-up interval is usually 6 months, involving the breast(s) containing the probably benign finding(s). Assuming stability at this 6-month examination, a category 3 assessment again will be rendered with a management recommendation for a second short-interval follow-up examination in 6 months but now involving both breasts if the opposite breast will be due for routine annual screening. Again assuming stability at this second short-interval follow-up, the examination is once more assessed as category 3, but now the recommended follow-up interval usually is lengthened to 1 year due to the already-observed 12-month stability. The recommended 2- or 3-year follow-up in these cases is 6 months, 6 months, 1 year, and, optionally, 1 more year to establish stability. After 2–3 years of stability, the finding should be assessed as benign (category 2). It should be emphasized that this approach is borrowed from mammography. While the vast majority of probably benign findings are managed with follow-up, there may be occasions in which biopsies are done instead (patient preference or overriding clinical concern). As with any interpretive examination, a less experienced reader may conclude that a finding such as benign BPE, for example, should be classified as category 3. A more experienced reader may recognize this as normal or benign at 6 or 12 months and classify it as category 1 or 2. With a properly worded report, the assessment category may then be changed to one that the current reader feels is appropriate, even though long-term stability has not been demonstrated.

It is imperative that surveillance imaging does not alter the stage at diagnosis or prognosis of the few patients with malignancies who are given category 3 assessments. Because this has not yet been demonstrated for MRI, as it has been for mammography, careful auditing of the use of category 3 assessments is necessary, and publication of outcomes data is strongly recommended. Although the data are not robust, it appears the ≤2% malignancy rate already demonstrated at mammographic follow-up also may be achieved at MRI. Several publications have demonstrated that focal lesions assigned to category 3 had a ≤2% malignancy rate, albeit without use of specific BI-RADS^® MRI descriptors for the lesions included in the studies. Publication of outcomes data for specific category 3 lesions, using BI-RADS^® MRI, is strongly recommended. It should be noted that a ≤2% malignancy rate may be difficult to achieve due to the high-risk population that usually is studied by MRI (higher than average prior probability of cancer).

A desirable goal for the frequency of making category 3 assessments at MRI is less than 10%. Over time, this rate should decrease to the point that a mature program should demonstrate a rate much closer to the approximately 1%–2% rate currently achieved at mammography, especially as the availability of previous examination(s) increases. A decrease in the frequency of category 3 assessments and false-positive outcomes has been demonstrated in the breast MRI literature as experience is gained.

Category 4: Suspicious. This category is reserved for findings that do not have the classic appearance of malignancy but are sufficiently suspicious to justify a recommendation for biopsy. The ceiling for a category 3 assessment is a 2% likelihood of malignancy, and the floor for a category 5 assessment is 95%, so category 4 assessments cover the wide range of likelihood of malignancy in between. Thus, almost all recommendations for breast interventional procedures will come from assessments made using this assessment category. In breast MRI, assessment category 4 is not currently divided into subcategories 4A, 4B, and 4C. Category 4 is used for the majority of findings prompting breast intervention, which can be performed by percutaneous biopsy, by US or stereotactic guidance, or by MRI guidance for lesions not visible at either US or mammography. As cysts rarely pose a problem in interpretation at MRI, diagnostic aspiration is not commonly performed. In many patients with a suspicious abnormality at MRI, targeted US will identify a corresponding abnormality so that US-guided biopsy can be performed. US-guided biopsies are faster, more comfortable for the patient, and more cost effective than MRI-guided biopsies. There are no established guidelines on who should undergo targeted US. However, in general, patients with masses larger than 5 mm should be examined by targeted US if the MR appearance is suspicious. Areas of NME may be evident on US as well, thus bringing the radiologist’s judgment into play. Factors that may limit visibility at US include fatty breasts, extremely complex breasts with multiple cysts, very large breasts, and very deep lesions. If there is any question about whether a presumed sonographic correlate actually is the same as the suspicious MRI lesion, MR-guided biopsy is advised.

Category 5: Highly Suggestive of Malignancy. These assessments carry a very high probability (≥95%) of malignancy. This category initially was established to include lesions for which 1-stage surgical treatment was considered without preliminary biopsy, in an era when preoperative wire localization was the primary breast interventional procedure. Nowadays, given the widespread acceptance of imaging-guided percutaneous biopsy, 1-stage surgery rarely if ever is performed. Rather, current oncologic management almost always involves tissue diagnosis of malignancy via percutaneous tissue sampling. This facilitates treatment options, such as when sentinel node biopsy is included in surgical management or when neoadjuvant chemotherapy isadministered prior to surgery. Therefore, the current rationale for using category 5 assessment is to identify lesions for which any nonmalignant percutaneous tissue diagnosis is considered discordant, resulting in a recommendation for repeat (usually surgical) biopsy. No single MRI descriptor is sufficiently predictive of malignancy to produce the ≥95% probability required for a category 5 assessment. Just as in mammography and US, an appropriate combination of suspicious findings is needed to justify a category 5 assessment at MRI. It is recommended that category 5 assessments be audited separately to verify a ≥95% PPV, thereby validating that the assessment is not being overused.

Category 6: Known Biopsy-Proven Malignancy. This category is reserved for examinations performed after biopsy proof of malignancy (imaging performed after percutaneous biopsy) but prior to surgical excision, in which there are no abnormalities other than the known cancer that might need additional evaluation. That is, a cancer diagnosis has already been established, a lesion is depicted at MRI, and this lesion corresponds to the previously biopsied cancer. A category 6 is not appropriate following successful lumpectomy or mastectomy (margin of resection free of tumor). The rationale for establishing category 6 is exclusion of these cases from auditing, because additional malignancy is frequently found such that auditing these cases would inappropriately skew overall outcomes. In the event that the breast with known cancer has a separate suspicious MRI finding that requires biopsy for diagnosis, the appropriate category 4 or 5 assessment should be rendered, and this would be the overall assessment because it leads to more prompt intervention.

BI-RADS lexicon for echography is a little bit different from the lexicon for mammography, thus the US report should have the following structure:

• 1. Indication for examination

• 2. Statement of scope and technique of breast US examination

• 3. Succinct description of the overall breast composition (screening only)

• 4. Clear description of any important findings

• 5. Comparison to previous examination(s), including correlation with physical, mammography, or MRI findings

• 6. Composite reports

• 7. Assessment

• 8. Management

• 1. Indication for Examination

  The reason for performing the examination should be stated briefly at the beginning of the report. The most common indications for breast US are confirmation and characterization of a palpable mass or mammographic or MRI abnormality, guidance of interventional procedures, and as the initial imaging technique for young, pregnant, or lactating patients. Additional applications are listed in the ACR Practice Guideline for the Performance of the Breast Ultrasound Examination and include the extent of disease evaluation supplementing mammography in high-risk women who are not candidates for breast MRI or who have no easy access to MRI and in breast imaging practices that provide the service, supplementary whole-breast screening in order to increase cancer detection in asymptomatic women with mammographically dense breasts.

• 2. Statement of Scope and Technique of Breast US Examination

  The scope of examination and technique used should be stated, for example, whether the examination was directed or targeted to a specific location or whether it was performed for supplementary screening. It is important, since US is a real-time examination, to indicate who performed the examination (sonographer, sonographer and physician, physician alone) or whether an automated whole-breast scanning system was used. If a lesion was evaluated with color or power Doppler or with strain or shear wave elastography, observations relevant to the interpretation should be reported. In certain situations, it may be beneficial to describe the position of the patient during the examination (e.g., “The breasts were imaged in both supine and lateral decubitus position” or “The patient was imaged in seated position, the position in which she feels the left breast thickening best”).

  Automated whole-breast scanners that acquire in 3D are available for clinical use and can be formatted in three planes. These scanners depict the entire breast in coronal, transverse, and sagittal planes, with the coronal view similar to the coronal MRI view. Reporting of these studies continues to evolve, but where possible the interpretation structure outlined previously and the reporting procedures described earlier in this section should be followed.

• 3. Succinct Description of the Overall Breast Composition (Screening Only)

  Tissue composition patterns can be estimated more easily in the large FOVs of automated US scans but can also be discerned in the small FOV of a handheld US scan. The three US descriptors for tissue composition described earlier in the US lexicon, “homogeneous background echotexture-fat,” “homogeneous background echotexture-fibroglandular,” and “heterogeneous background echotexture” (below), correspond loosely to the four density descriptors of mammography and the four fibroglandular tissue descriptors of MRI. At US, breast tissue composition is determined by echogenicity. Subcutaneous fat, the tissue relative to which echogenicity is compared, is medium gray and darker than fibroglandular tissue, which is light gray. Heterogeneous breasts show an admixture of hypoechoic and more echogenic areas. Careful real-time scanning will help differentiate a small hypoechoic area of normal tissue from a mass.

  • (a) Homogeneous background echotexture-fat

  • (b) Homogeneous background echotexture-fibroglandular

  • (c) Heterogeneous background echotexture

• 4. Clear Description of Any Important Findings

  The description of important findings should be made, in order of clinical relevance, using lexicon terminology, and should include:

  • (a) Characterization of a mass using the morphological descriptors of shape, margin, and orientation. Note should be made of the lesion’s effect on the surrounding tissue, such as architectural distortion. Feature categories, such as posterior features and echogenicity, and techniques, such as color or power Doppler and elastography, may contribute information to the analysis, but only pertinent positives need to be described. Recognition of special case findings, such as simple and complicated cysts, clustered microcysts, intramammary lymph nodes, and foreign bodies, should simplify interpretation. In reporting screening examinations in asymptomatic women, as in mammography, characteristically benign findings may be reported (assessment category 2), but it is not obligatory, and the appropriate assessment would then be negative (assessment category 1).

  • (b) For important findings, lesion size should be given in at least two dimensions; three dimensions are preferable, especially if the volume of a mass is compared with one or more previous examinations. It is not necessary to report the measurements of every small simple cyst, and if numerous cysts are present, especially in both breasts, location and measurements of the largest cyst in each breast will suffice. If a mass is measured, images should be recorded with and without calipers. Marginal characteristics are one of the most important criteria to be applied in assessing the likelihood of malignancy of a mass, and, particularly with small masses, caliper markings may obscure the margin, hindering analysis.

  • (c) Location of the lesion(s) should be indicated using a consistent and reproducible system, such as clock-face location and distance from the nipple. When more than one mass or abnormality is located in the same scan frame or in the same locale, measurement of the distance from the skin to the center of the mass or its anterior aspect may help to differentiate one lesion from another. This measurement may be particularly useful when one mass is singled out for biopsy and others are depicted in the field. There may be variability within breast imaging practices, and members of a group practice should agree upon a consistent policy for documenting lesion location on subsequent examinations. In some practices, for all examinations that follow the initial US study, the lesion location annotation will be repeated without change. Other breast imagers may report a different location to signify the same lesion but indicate in their reports that the lesion is now seen at another clock-face position and distance from the nipple (these differences are often related to positioning and technique).

  • (d) As at mammography, multiple bilateral circumscribed masses usually are assessed as benign (category 2) unless one mass has different imaging features than all the others. In the unusual circumstance in which the interpreting physician chooses to describe multiple benign-appearing masses individually within the US report, the masses should be listed by breast, by location within in the breast, and by size. The reader of the report will be less confused, and, if surveillance is suggested as management, the performer of the subsequent examination will appreciate a list rather than verbose text. For bilateral findings, describe all the findings in each breast in a separate paragraph.

• 5. Comparison to Previous Examination(s), Including Correlation with Physical, Mammography, or MRI Findings

  Breast US should be correlated with physical findings, mammography, MRI, or other imaging studies, if performed. If no statement of comparison is included in the US report, it will be assumed that no comparison was made. Note that some report templates include a “comparison” heading, in which the word “none” (if appropriate) may be entered. When correlating US findings with those seen at mammography and/or MRI, the operator performing handheld scanning should correlate the size and location of lesions and match the type and arrangement of tissues surrounding the lesion in order to reduce the likelihood of misregistration (identifying a different lesion or lesions at different imaging modalities). In doing this, allowance for positional changes should be made going from upright with mammography and prone with MRI to supine or supine-oblique with US. If it is determined that a sonographic finding corresponds to a palpable abnormality or to a mammographic or MRI finding, this should be stated explicitly in the US report. If the US finding is new or has no correlate, this should also be stated in the report. If the US examination was performed as part of a surveillance protocol to assess a previously identified finding, or if the finding was reported on a previous examination, the current report should describe any changes. An increase of 20% or more in the longest dimension of a probably benign solid mass within 6 months may prompt biopsy. 1 An increase of only 1–2 mm in lesion size may be related to differences in scanning technique or patient positioning.

• 6. Composite Reports

  When more than one type of examination is performed concurrently (on the same day), it is preferable that the examinations be reported together. The findings for each examination should be described in separate paragraphs with an overall assessment and management recommendations for the combined examinations. In general, when the assessments for two examinations differ, the overall assessment (and concordant management recommendations) should reflect the more abnormal of the individual assessments (whatever management is expected to come first, supplemented by likelihood of malignancy), according to the following hierarchy of increasing abnormality: categories 1, 2, 3, 6, 0, 4, and 5 (Table 1.7). Exceptions to this rule occur when the characteristically benign features of a given imaging finding on one examination supersede the less specifically benign features of the same finding on the other examination. An example is that of a partially circumscribed, noncalcified mass at mammography, superseded by simple cyst at US.

Table 1.7 Abnormality hierarchy

• 7. Assessment

  The report should conclude with a concise summary of pertinent US findings with a final assessment using BI-RADS^® US categories 1–6 and the phrases associated with them. If report of a US examination is integrated with that of a concurrently performed mammography examination, the combined final assessment should reflect the highest likelihood of malignancy assessed at the two examinations. Clear and consistent communication is a goal that can be achieved for breast US by using the same assessment categories and similar wording described in the BI-RADS^® Mammography section. In some cases, the interpreting physician may render an incomplete assessment (category 0) in order to request additional examination(s), such as mammography, comparison with previous but currently unavailable examinations, or additional physician-performed real-time scanning after either a sonographer-produced, real-time, or automated whole-breast screening US examination.

  BI-RADS categories used in echography analysis corresponds to the categories used in other diagnostic procedures (Sect. 6.6 in Chap. 6).

• (a) Assessment Is Incomplete

Category 0: Incomplete—Need Additional Imaging Evaluation and/or Prior Images for Comparison. There is a finding for which additional imaging evaluation is needed. This is almost always used in a screening situation. In this context, additional imaging evaluation includes the recording of (nonstandard) US images to supplement the standard images recorded for a screening examination. Note that this does not include repeat real-time scanning by the interpreting physician and/or colleague as long as additional images are not recorded. This respects the unique real-time nature of US and does not penalize its use. Under certain circumstances, assessment category 0 may be used in a diagnostic US report, such as when equipment or personnel are not immediately available to perform a needed concurrent diagnostic mammography examination or when the patient is unable or unwilling to wait for completion of a full diagnostic examination. Category 0 should not be used for diagnostic breast imaging findings that warrant further evaluation with MRI. Rather, the interpreting physician should issue a final assessment in a report that is made before the MRI examination is performed. In most circumstances and when feasible, if a screening US examination is not assessed as negative or benign, the current examination should be compared to prior examination(s), if any exist.

The interpreting physician should use judgment on how vigorously to attempt obtaining prior examinations, given the likelihood of success of such an endeavor and the likelihood that comparison will affect the final assessment. In this context, it is important to note that comparison to previous examination(s) may be irrelevant when a finding is inherently suspicious or malignant. Category 0 should be used for prior image comparison only when such comparison is required to make a final assessment. When category 0 is used in the context of awaiting prior examinations for comparison, there should be in place a tracking system guaranteeing with 100% reliability that a final assessment will be made within 30 days (preferably sooner), even if prior examinations do not become available. Some breast imaging practices may reasonably choose never to use category 0 in the context of awaiting prior examinations simply because they do not have a 100% reliable tracking system. If an US examination is assessed as category 0 in the context of awaiting prior examinations and then the prior examinations do become available, an addendum to the initial US report should be issued, including a revised assessment. For auditing purposes, the revised assessment should replace the initial assessment. A need for previous studies to determine appropriate management might also temporarily defer a final assessment.

• (b) Assessment Is Complete—Final Categories

Category 1: Negative. There is nothing to comment on. This is a normal examination.

Category 2: Benign. As with category 1, this is a “normal” assessment, but here the interpreter chooses to describe a benign finding in the US report. For example, the interpreter may choose to describe one or more simple cysts, intramammary lymph nodes, postsurgical fluid collections, breast implants, or complicated cysts/probable fibroadenomas that are unchanged for at least 2 or 3 years while still concluding that there is no sonographic evidence of malignancy. On the other hand, the interpreter may choose not to describe such findings, in which case the examination should be assessed as negative (category 1). Note that both category 1 and category 2 assessments indicate that there is no sonographic evidence of malignancy. Both should be followed by the management recommendation for routine age-appropriate screening. The difference is that category 2 should be used when describing one or more specific benign sonographic findings in the report, whereas category 1 should be used when no such findings are described (even if such findings are present).

Category 3: Probably Benign. Category 3 assessment, probably benign, is not an indeterminate category for use simply when the radiologist is unsure whether to render a benign (BI-RADS^® category 2) or suspicious (BI-RADS^® category 4) assessment, but one that is reserved for specific imaging findings known to have >0% but ≤2% likelihood of malignancy. For US, there is robust evidence that a solid mass with a circumscribed margin, oval shape, and parallel orientation (most commonly fibroadenoma), and an isolated complicated cyst have a likelihood of malignancy in the defined (≤2%) probably benign range, for which short-interval (6-month) follow-up sonography and then periodic sonographic surveillance may represent appropriate management. Similar data have been reported for clustered microcysts, but these data are less strong because they involve many fewer cases. The use of category 3 assessment for sonographic findings other than these three should be considered only if the radiologist has personal experience to justify a watchful-waiting approach, preferably involving observation of a sufficient number of cases of an additional sonographic finding to suggest a likelihood of malignancy within the defined (≤2%) probably benign range. This edition of the BI-RADS^® Atlas also emphasizes the recommendation that a category 3 assessment should not be made at screening; rather, this should be done only after completion of a full diagnostic breast imaging examination. This recommendation is appropriate for screening mammography, for which batch interpretation usually is utilized, because in this setting there is no opportunity to complete the diagnostic workup before interpreting the screening examination. However, screening US almost always is interpreted online, so a full diagnostic examination also is completed while the patient remains in the breast imaging facility, and a single breast imaging report may be issued that combines the findings of both screening and diagnostic components of the examination. Hence, there is no purpose in recommending against category 3 assessment at screening US because the diagnostic workup would be completed simultaneously. Note that for auditing purposes, the screening component of a category 3-assessed screening US examination will be audit-positive, not only because additional nonstandard (diagnostic) images will be recorded but also because a category 3 assessment at screening is defined as being audit-positive. For category 3 assessments, the initial short-term follow-up interval is usually 6 months, involving the breast(s) containing the probably benign finding(s). Assuming stability at this 6-month examination, a category 3 assessment again is rendered with a management recommendation for a second short-interval follow-up examination in 6 months. Again assuming stability at this second short-interval follow-up, the examination is once more assessed as category 3, but now the recommended follow-up interval usually is lengthened to 1 year due to the already-observed 12-month stability. Note that although the 1-year follow-up coincides with the routine screening interval in the USA, a category 3 assessment is rendered, to indicate that the period of imaging surveillance is still underway. As with surveillance using mammography, after 2–3 years of stability, the final assessment category should be changed to benign (BI-RADS^® category 2). A benign evaluation may also be rendered before completion of category 3 analysis if, in the opinion of the interpreter, the finding has no chance of malignancy and is thus a category 2.

Category 4: Suspicious. This category is reserved for findings that do not have the classic appearance of malignancy but are sufficiently suspicious to justify a recommendation for biopsy. The ceiling for category 3 assessment is a 2% likelihood of malignancy, and the floor for category 5 assessment is 95%, so category 4 assessments cover the wide range of likelihood of malignancy in between. Thus, almost all recommendations for breast interventional procedures will come from assessments made using this category. By subdividing category 4 into 4A, 4B, and 4C, as recommended in and using the cut points indicated in the Guidance chapter, it is hoped that patients and referring clinicians will more readily make informed decisions on the ultimate course of action. An example of separating the BI-RADS assessment category from the management recommendation (new to fifth edition—see Follow-up and Outcome Monitoring section) occurs when a simple cyst, correctly assessed as BI-RADS 2, undergoes cyst aspiration for pain control.

Category 5: Highly Suggestive of Malignancy. These assessments carry a very high probability (≥95%) of malignancy. This category initially was established to involve lesions for which 1-stage surgical treatment could be considered without preliminary biopsy in an era when preoperative wire localization was the primary breast interventional procedure. Nowadays, given the widespread acceptance of imaging-guided percutaneous biopsy, 1-stage surgery rarely if ever is performed. Rather, current oncologic management almost always involves tissue diagnosis of malignancy via percutaneous tissue sampling to facilitate treatment options, such as when sentinel node imaging is included in surgical management or when neoadjuvant chemotherapy is administered prior to surgery. Therefore, the current rationale for using a category 5 assessment is to identify lesions for which any nonmalignant percutaneous tissue diagnosis is considered discordant, resulting in the recommendation for repeat (usually vacuum-assisted or surgical) biopsy. Also note that whereas the fourth edition simply indicated that “appropriate action should be taken” as management for category 5 assessments, the fifth edition provides the more directed management recommendation that “biopsy should be performed in the absence of clinical contraindication.” This new text unequivocally specifies tissue diagnosis as the interpreting physician’s management recommendation for category 5 assessments, appropriately and effectively transferring the burden of establishing a contraindication to this recommendation to the referring clinician.

Category 6: Known Biopsy-Proven Malignancy. This category is reserved for examinations performed after biopsy proof of malignancy (imaging performed after percutaneous biopsy but prior to surgical excision), in which there are no abnormalities other than the known cancer that might need additional evaluation.

The use of the BI-RADS system, with X-ray, ultrasound, and MR imaging, facilitates communication between radiologists and clinicians resulting in increased accuracy of diagnosis and better treatment outcomes.

The following breast cancer screening algorithm is recommended (Fig. 1.24):

• 1. In order to timely detect breast pathology, US is mostly used as a supplementary test in women aged ≤49 years.

• 2. During preventive medical check-ups aimed at timely diagnosis of breast pathology, annual breast US should be performed in 20–39-year-old women in addition to physical examination.

• 3. In 40–49-year-old women, mammography should be performed every other year. Breast US is carried out in the intervals between mammography.

• 4. In women of the age 50 years and older, as a rule, mammography is performed every other year.

Fig. 1.24

The flowchart of screening programs with US

Inclusion of the ultrasound method in the complex breast cancer screening algorithm will make it possible to balance out the drawbacks of the X-ray method in women with dense breast and to conduct a complete breast examination in women under the age of 40. This will allow the detection of not only malignant tumors but also benign proliferative breast diseases, which may cause breast cancer development in many cases.

Imaging techniques became very important for early and differential diagnosis of breast diseases. Successful implementation of screening programs and reasonable combination of traditional and innovative technologies facilitate the work of radiologists, mammologists, oncologists, surgeons, and endocrinologists and permit detection of a wide range of breast diseases at early stages, to choose effective treatment methods, specify prognosis, and determine rational terms of follow-up.