Screening programmes enable the detection of early asymptomatic cancers [1]. Among cancers detected in the second round of the English bowel cancer screening pilot, 17.7 % were polyp cancers. However, cancer risk stratification in bowel cancer screening programme (BCSP) patients based on endoscopic polyp size has not been reported [2]. Accurate marking (tattooing) of lesions suspected of malignancy at colonoscopy is recommended [3, 4]. This is increasingly important as patients requiring surgical treatment are frequently offered laparoscopic surgery and the lack of tactile feedback can prevent tumour localisation, increasing the potential risk of resection of the wrong bowel segment [5]. Furthermore, if a polypectomy has been performed, there may be no obvious abnormality left to aid detection at surgery except for a tattoo. Where tattooing was not performed, a repeat colonoscopy preoperatively may become necessary adding to the overall cost.

Current guidelines recommend tattooing of suspicious-looking lesions without reference to the size of the polyp [3, 4]. The endoscopist has to judge which lesion may be malignant and require future localisation based on the appearance and size of the polyp.

The aim of this study was to determine the relationship between endoscopic polyp size and invasive colorectal cancer in order to inform tattooing practice for patients taking part in the national BCSP.

Patients and methods

Data were collected retrospectively from a prospectively maintained database of BCSP patients who had undergone polypectomy between October 2008 and October 2010. All patients were asymptomatic with a positive faecal occult blood (FOB) test. Histology was obtained from electronic patient records. Data were analysed using SPSS ver. 15.0 (SPSS, Inc., Chicago, IL). Spearman’s correlation coefficient and the χ2 test were used for statistical analysis.

Results

During the study period, 269 polypectomies were performed in 165 BCSP patients. The mean age was 66 years and 66 % were men. At colonoscopy, polyps appeared sessile in 67 % (182/269) and pedunculated in 33 % (87/269). The risk of malignancy and high-grade dysplasia was similar for the two types (Table 1).

Table 1 Cancer/high-grade dysplasia risk stratification according to polyp type
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The majority of the polyps were left-sided (56 %, 151/269), 30 % (81/269) were right-sided, and 14 % (37/269) were in the rectum. Histologically, 81 % (219/269) of the polyps were neoplastic (Fig. 1). The dysplastic grade was low in 95 % (210/219) and high in 5 % (11/219). Two of the 11 polyps with high-grade dysplasia were right-sided. Eight polyps were found to contain invasive malignancy and most of them (75 %, 6/8) were situated in the left hemicolon or rectum. The proportion of cancer and high-grade dysplasia was higher in polyps found on the left side of the bowel compared to the right side, but this difference was statistically not significant (Table 2; p = 0.447). The mean (±SD) endoscopic polyp size (10.7 ± 8 mm) was greater than that at histological assessment (9.6 ± 6 mm). The endoscopic and pathological polyp size correlated well (Spearman’s rho = 0.736; p < 0.001).

Fig. 1
figure 1

Types of polyps

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Table 2 Risk of cancer/high-grade dysplasia according to site
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The risk of malignant change within a polyp was 0.7 % (1/143) when the endoscopic polyp size was <10 mm; the risk increased to 2.4 % (2/83) when the polyp size was 10–19 mm and was 13 % (5/40) when >19 mm. This was statistically significant (p = 0.001). A similar trend was noted for high-grade dysplasia and size (Table 3).

Table 3 Cancer/high-grade dysplasia risk stratification according to endoscopic size
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Overall, 23 % (38/165) of the patients had a colonic lesion tattooed; the mean size of the polyps in this subgroup was 21 mm (range = 15–50 mm). Therefore, 25 % of the malignant polyps and 63 % of the polyps with high-grade dysplasia were not tattooed.

Discussion

Precise localisation of colonic lesions is important for their identification at repeat examination or subsequent surgery. The colonic lesions of up to 21 % of patients may be erroneously localised at endoscopy and use of tattooing techniques has been recommended to avoid this [6, 7]. Identifying lesions that may need further treatment or monitoring, thus requiring a tattoo, is an imprecise science and based on appearance and size of the polyp.

Various techniques and markers have been used to mark colonic lesions for subsequent examination or surgery [8, 9]. Submucosal injection of India ink is an inexpensive, safe, and an effective method for tumour localisation in laparoscopic colorectal surgery [10]. The European guidelines for cancer screening recommend that India ink tattooing should be performed distal to the lesion, and should include at least three quadrants of the bowel [3].

Not all patients who undergo a polypectomy have the site tattooed. This may be for a number of reasons, including concerns about longer procedure time, risk to the patient, and the increased cost of the procedure. One study reported that only 65 % of the BCSP patients who underwent laparoscopic resection had their colonic lesion tattooed [11]. About 23 % of the patients in this study received a colonic tattoo, with the smallest polyp size being 15 mm. Consequently, 25 % of the malignant polyps and 63 % of polyps with high-grade dysplasia were not tattooed.

Tattooing of lesions suspected of malignancy is recommended in order to facilitate easy localisation at surgery or endoscopic follow-up. Failure to do so will lead to uncertainty which may result in patient harm [12]. Furthermore, polyps that do not lift at the time of tattooing are likely to be advanced in nature and potentially not suitable for endoscopic resection [13].

The factors that guide the endoscopist’s decision to tattoo are the appearance and size of the polyp. Most malignant polyps have a benign appearance at endoscopy [14] so a decision has to be based on polyp size. Whilst the majority of polyps detected in this study were <10 mm and benign, the risk of malignancy was 5.6 % (7/123) in polyps >10 mm. These results are similar to those found in the French screening programme [15]. The risk of polyp cancer among BCSP patients increases significantly when the endoscopic polyp size is ≥10 mm. Based on this study we recommend that all polyps ≥10 mm should be tattooed.