Keywords

General Considerations

Tumors in the maxillofacial region can arise in the soft and hard tissues. Those located in the facial skeleton are rare and can be of odontogenic or osseous origin. No matter whether they are benign or malignant, clinically they are often symptomless for a long time. Even radiologically, their appearance is mostly uniform and lytic. Most lesions expand the jawbones over time, and patients notice painless swellings or facial deformity. Size generally does not help in the differential diagnosis. Delineation, intralesional matrix mineralization and the exact site of origin on the other hand are important clues to the correct diagnosis [1,2,3]. Although computed tomography (CT) or magnetic resonance imaging (MRI) is much more precise in characterizing the content and delineation of tumors, in most cases it is not possible to establish a diagnosis without biopsy and histologic examination. Biopsies should always be obtained as open biopsies to receive sufficient material in quantity and quality. This is particularly important since some lesions can present histologically similar or can be affected by metaplastic changes due to secondary inflammation which can blur the diagnostic hallmarks. The key to an adequate diagnosis is a close interdisciplinary collaboration between the clinician, the pathologist, and the radiologist. The treatment plan is, of course, crucially dependent on a precise preoperative diagnosis.

Fig. 7.1
figure 1

Cystic lesion in the left mandibular angle with a retained molar. The x-ray appears similar to a dentigerous cyst. Histologically, a unicystic ameloblastoma was identified

Full size image
Fig. 7.2
figure 2

Epithelial islands of an ameloblastoma are found to infiltrate the bony structures

Full size image
Fig. 7.3
figure 3

Extensive polylobulated lesion in the left ramus and mandibular angle of an 18-year-old man. The swelling was painless and the patient did not notice a loss of sensitivity in his left lower lip. Diagnosis: odontogenic keratocyst

Full size image
Fig. 7.4
figure 4

Although the lesion was very extensive and reached into the area of the joint, conservative treatment with curettage and filling of the cavity with autogenous cancellous bone was performed. The patient will remain in a follow-up control for many years

Full size image
Fig. 7.5
figure 5

Polylobulated lesion in the left mandibular retromolar and angle area. Diagnosis: conventional ameloblastoma

Full size image
Fig. 7.6
figure 6

Reconstruction of the mandibular defect with a reconstruction plate and an autologous bone graft taken from the iliac crest

Full size image
Fig. 7.7
figure 7

Two years after the reconstruction, the reconstruction plate was removed and dental implants inserted

Full size image
Fig. 7.8
figure 8

Extensive lytic lesion in the right horizontal part of the mandible surrounding the roots of the teeth 44, 45, 46, and 47. All teeth were found to be vital. Diagnosis: central giant cell granuloma

Full size image
Fig. 7.9
figure 9

After careful curettage of the lesion and defect filling with autogenous cancellous bone, only tooth 47 lost its vitality

Full size image
Fig. 7.10
figure 10

Osteosarcoma of the maxilla with typical radiologic appearance on CT and MR (a, b)

Full size image
Fig. 7.11
figure 11

Osteosarcoma of the left body of the mandible. First symptom of the patient was a small anesthetic buccal skin region. After enlargement of the anesthetic area and dental treatment, first bone biopsy was taken in clinic after approximately 6 months. Osteolytic region in conventional x-ray (a). (b) CT, MRT findings showing extension of the lesion into the buccal soft tissue (c) Wide bony resection including buccal skin reconstruction of soft tissues with a microvascular latissimus dorsi flap (d). After obtaining the definitive histology and clear bony margins additionally microvascular bone reconstruction with fibular graft tailored with bone guides and patient-specific implant (KLS Martin, Tuttlingen, Germany) (e, f) Postoperative x-ray of the patient 10 days after fibular grafting (g)

Full size image

Odontogenic Tumors and Tumorlike Lesions

Tumors and tumorlike lesions of odontogenic origin are less common than those of osseous origin. Most cases resemble stages of the physiological development of teeth. Because epithelial and mesenchymal tissues are involved in the formation of the tooth bud, both components can also be involved in the differentiation of an odontogenic tumor. Most odontogenic tumors are benign, and some rather represent tumorlike lesions or hamartomas, such as odontomas. Therefore, most are clinically, radiologically, and histologically well delineated and can be treated by curettage, enucleation, or sometimes fenestration. Their radiologic appearance is mostly uniform and often resembles dentigerous cysts (Fig. 7.1). An infiltrative pattern of growth into the surrounding bone is observed only in a smaller subset of tumors, including ameloblastoma (Fig. 7.2) and odontogenic myxoma [2].

Because of the size and location of some benign lesions, such as odontogenic keratocysts, odontogenic myxomas, or adenomatoid odontogenic tumors, it may be necessary to perform a complete resection of the involved bone and a reconstruction thereafter [4]. Table 7.1 lists the current classification of benign odontogenic tumors and tumorlike lesions. Selected cases are shown in Figs. 7.3 and 7.4.

Table 7.1 Benign odontogenic tumors and tumorlike lesions
Full size table

Conventional ameloblastoma is a locally aggressive tumor that requires a complete resection with clear margins. With the exception of the luminal and intraluminal variant of the unicystic subtype, neither radiologic characteristics, such as mono- or multilocular appearances, nor resorption of tooth roots allows to differentiate between clinically more or less aggressive tumors. Initially, resorption of tooth roots has been regarded as pathognomonic for ameloblastomas. Meanwhile, this phenomenon has been observed in various lesions, including several odontogenic cysts, and has been demonstrated not to indicate a higher aggressiveness of the lesion [5]. Table 7.2 shows a list of lesions in which radiologically resorptions of tooth roots can be observed. Although in rare instances ameloblastoma patients can develop metastases (so-called metastasizing ameloblastoma) or convert into an ameloblastic carcinoma, neck dissection is generally not recommended.

Table 7.2 Lesions with possible tooth root resorption on x-rays
Full size table

Ameloblastomas are predominantly located in the (posterior) mandible and with the exception of unicystic ameloblastoma rarely develop before the age of 20. They do not produce any kind of matrix and therefore radiologically always appear purely lytic. Both aspects can serve as important clues in the differential diagnosis with radiological mimics. Lately, ameloblastoma has been demonstrated to consistently show point mutations in the MAP kinase signaling pathway with BRAF (p.V600E) being most commonly affected (approximately 60% of cases) [6, 7].

In most instances, after complete resection of the tumor, a primary reconstruction with a reconstruction plate and a free bone graft is performed. Only rarely and depending on the size and location of the defect is a primary reconstruction with a microvascular graft indicated. The most important precondition for a successful primary reconstruction is a reliable stabilization with plates and screws together with a reliable closure of the soft tissues around the grafts as demonstrated in the following case:

A 41-year-old patient presented with a symptomless moderate swelling of his left mandibular angle area. On x-ray, a polylobulated lesion was found, and after an open biopsy, a conventional ameloblastoma was diagnosed. After resection of the tumor through a partial mandibulectomy, the defect was bridged with a 2.7 reconstruction plate. A bone graft was taken from the iliac crest and the bony defect immediately reconstructed. Two years after the resection of the tumor, the plate was removed on the patient’s request. As a rule we do not remove these plates because they are not responsible for any resorption of the bone graft through stress protection. At the occasion of the plate removal, dental implants were inserted into the bone graft (Figs. 7.5, 7.6 and 7.7).

Nonodontogenic Tumors and Tumorlike Lesions Within the Facial Bones

Mesenchymal tumors in the jaws show distinct characteristics compared with their counterparts in the peripheral skeleton. They are less often benign than odontogenic tumors. Some develop almost exclusively in the craniofacial bones, such as osteoma and central giant cell granuloma (CGCG), while others, such as conventional giant cell tumor of bone (GCT), are very rare to nonexistent in the gnathic bones. Whereas a relationship between CGCG and GCT has long been debated, it has become clear in the last years that they indeed represent independent and distinct entities, since GCT consistently show point mutations in the H3F3A gene and CGCG do not [8]. For CGCG, an important diagnostic sign is the vitality of the adjacent teeth. They often remain vital although their roots reach into the lytic lesions (Figs. 7.8 and 7.9).

The establishment of a special registry for tumors of the craniofacial skeleton in 1971 by the German-Austrian-Swiss Association for the Study of Tumors of the Face and Jaws (DÖSAK) was enabled to collect and document these rare lesions systematically and to also draw conclusions regarding their distribution and clinico-pathological features. Long before the detection of H3F3A mutations, the distinction of CGCG and GCT as separate entities therefore already seemed obvious on morphological reasons only.

The majority of benign non-odontogenic tumors are exceptionally rare and can be divided into bone- and cartilage-forming, fibro-osseous, giant cell-containing, vascular, and hematolymphoid lesions. Radiographically, most of the tumors appear lytic with varying degrees of intralesional matrix mineralization. As in odontogenic tumors, a biopsy is usually required to establish the diagnosis with the exception of typical cemento-osseous dysplasia or craniofacial fibrous dysplasia. Table 7.3 lists the most common benign and non-odontogenic lesions in the facial skeleton.

Table 7.3 Benign and non-odontogenic tumors and tumorlike lesions
Full size table

Radical excision is necessary for all cartilaginous lesions because of a strong tendency for recurrence. Resection or enucleation is sufficient for osteoma, osteoblastoma, ossifying fibroma, central giant cell granuloma, and aneurysmal bone cysts [3]. A simple bone cyst is an empty (or blood-filled) cavity without an epithelial lining. Apparently, the opening and the subsequent bleeding into the cavity initiate reossification of the area.

Surgical contouring, or in smaller lesions enucleation, is the treatment of choice for fibrous dysplasia. Because of the tendency for recurrence or regrowth, clinical and radiologic follow-up for many years is indicated. Malignant transformation is very rare and sometimes associated with radiotherapy.

Although desmoplastic fibroma may be considered as locally aggressive and its growth pattern may be infiltrative into the cancellous areas of the bone, a first operative step can be enucleation for those well delineated on x-rays and more radical resection for those not well demarcated or in the case of recurrence.

Generally, radiotherapy is not indicated for any of the abovementioned lesions. On the contrary, radiotherapy may be harmful since it may cause malignant transformation into osteosarcoma.

Osteosarcomas of the jaws are also rare but differ decisively from tumors of the peripheral skeleton. They typically occur one or two decades later in life (third–fourth decade) and metastasize significantly less frequently (6–21%) and usually only after a protracted course. Most cases therefore can probably be cured by complete resection with clear margins although there is a subset of more aggressive tumors for which no markers have been identified yet. Some groups therefore recommend to treat high-grade tumors by additional (neo-)adjuvant chemotherapy, the crucial importance of free surgical margins, however, remains indisputable. The favorable prognosis is restricted to tumors of the jaws, whereas osteosarcomas of the remaining craniofacial bone have an equally limited chance of cure than peripheral tumors. Chondroblastic osteosarcoma is far more frequent in the jawbones than chondrosarcoma which should be kept in mind when a diagnosis of chondrosarcoma is made on biopsy material [1] (Figs. 7.10 and 7.11).