Jaw swelling is most often caused by developmental enlargements (e.g. tori or exostoses), which are benign, painless, broad-based and self-limiting, usually with normal overlying mucosa and typically require no intervention.
Aneurysmal bone cyst is a rare lesion, which is actually not a cyst. The aetiology remains obscure: approximately one-third appear to be associated with other bone disorders, such as a giant cell lesion, fibrous dysplasia and ossifying fibromas. This rare lesion presents as an asymptomatic hard swelling of the jaw, sometimes following a history of trauma. It may occur in any part of the skeleton. Radiographs show a unilocular, or multilocular translucency with a honeycomb or soap-bubble appearance. Preoperative aspiration shows bloody fluid with a low haematocrit, differentiating it from undiluted blood in a vascular anomaly, such as haemangioma. Diagnosis is confirmed by histology, which shows numerous capillaries and blood-filled spaces, areas of haemorrhage associated with multinucleated giant cells and irregular areas of osteoid. Treat by thorough curettage or excision.
Cherubism is a rare genetically determined jaw disease, which closely resembles fibrous dysplasia except for the autosomal dominant inheritance (but variable expression) and association with chromosome 4p and mutated gene SH3BP2 which codes for a c-abl-binding protein. Painless symmetrical enlargement at the angles of the mandible and in the maxilla leads to the typical ‘cherubic’ facial appearance. Cherubism presents at 2–4 years of age, lesions growing progressively until puberty when they arrest or regress. Expansion of the alveolar bone results in irregular spacing and premature loss of teeth and possibly disturbances to a developing dentition. Imaging shows well-defined multilocular radiolucencies in the mandible, but maxillary lesions are less clearly defined. Blood chemistry is normal, although there may a raised alkaline phosphatase during active growth periods. Histologically, the lesions consist of loose vascular connective tissue with numerous multinucleated giant cells and, as in fibrous dysplasia, there is fibrous replacement of bone (Fig. 16.1). Other fibro-osseous lesions and giant cell lesions of bone (giant cell granuloma, hyperparathyroidism, giant cell tumours) should be excluded. Treatment of cherubism is as for fibrous dysplasia (see also Noonan syndrome, Ch. 56).
Bone prominences are not uncommon in the jaws and are given different names which are site-specific. Torus palatinus is found only in the midline of the hard palate (see below). Torus mandibularis is found only on the lingual surface of the mandible, near the premolar teeth. Buccal exostosis is found only on the facial surface of the alveolar bone, usually in the maxilla. Exostoses typically appear in early adulthood, are painless and may slowly enlarge over time. Bone prominences usually require no treatment, and have no malignant potential.
Bony proliferations in other sites are considered to be usually either trauma-induced inflammatory periosteal reactions (exostoses), or true neoplasms (osteomas). Unless such a bony prominence is specifically located, is pedunculated or is associated with an osteoma-producing syndrome such as Gardner syndrome (Ch. 56), there is no way to differentiate exostosis from osteoma, even histopathologically.
Fibrous dysplasia is an uncommon disorder characterized by the replacement of an area of bone with fibrous tissue. Mutations in signalling protein gene GNAS 1 may be involved. Fibrous dysplasia usually presents as a painless bony hard swelling, most often in a child and in the maxilla or adjacent bones. The maxillary sinus is often involved, when there may be encroachment on the orbit (causing proptosis) and nasal cavity (causing obstruction). Expansion of the alveolar bone leads to disruption of occlusion, displacement of teeth and possibly failure of eruption of teeth. Lesions appear to stabilize with skeletal maturation.