FIBROMATOSIS

The fibromatoses represent a group of infiltrating fibrous proliferations with a biologic behavior and microscopic appearance intermediate between those of benign fibrous lesions and fibrosarcomas. In the head and neck region, they are sometimes referred to as juvenile or aggressive juvenile fibromatoses. Patients of any age may be affected, but three quarters of all cases are diagnosed when the patient is younger than 10 years. No significant sex predilection is apparent.

The most frequent site of occurrence is the soft tissues adjacent to the mandible. Intraoral presentations are rare, but they most often involve the tongue or buccal mucosa. Lesions appear as firm, painless, poorly demarcated masses with a variable growth rate. They are locally aggressive and often cause resorption of the underlying bone when present. A desmoplastic fibroma occurring within the medullary cavity of bone is considered to be the intraosseous counterpart of the soft tissue fibromatosis.[16]

The differential diagnosis of a soft tissue fibromatosis is myofibroma and rhabdomyosarcoma.

Microscopically, fibromatosis is characterized by a poorly delineated, infiltrating cellular proliferation of mature spindle cells arranged in streaming and interlacing fascicles. Collagen production is usually prominent. Infiltration of the adjacent structures is common at the periphery, but cellular atypia is not present.

Treatment consists of wide excision. The reported recurrence rate of 24% for oral fibromatosis is considerably lower than the 50-70% rate reported for fibromatoses of the entire head and neck region.

Gingival fibromatosis deserves separate consideration. It may be hereditary, idiopathic, or drug induced. The hereditary and idiopathic forms manifest as isolated or diffuse firm, noninflammatory enlargements of the keratinized gingiva. Although the process is typically nonpainful, the enlarged gingiva may eventually cover large portions of the clinical crowns of teeth and erode the underlying bone. Recurrence is common following surgical excision. The hereditary form may also manifest as a component of a larger complex syndrome (eg, gingival fibromatosis with hypertrichosis syndrome, Zimmermann-Laband syndrome, Cross syndrome). Both the idiopathic and hereditary forms are rare, limited to the gingiva, and most often affect children. Drug-induced gingival overgrowth has been associated with systemic use of phenytoin, cyclosporin, and calcium channel blockers.