fibromatosis /-mətō″sis/ [L, fibra + Gk, oma, tumor, osis, condition] , 1. a gingival enlargement believed to be hereditary or idiopathic, manifested in the secondary dentition. It is characterized by a firm hyperplastic tissue that covers the surfaces of the teeth. Differentiation between this condition and phenytoin hyperplasia is based on a history of phenytoin ingestion. The gums consist of fibrous lesions that demonstrate an infiltrative growth pattern and aggressive clinical behavior. Histologically, it presents as dense hypocellular and hypovascular collagenous tissue, which forms interlacing bundles running in all directions. See also gingival hyperplasia. 2. a benign tumor of soft tissue. Should not be confused with neurofibromatosis.
