"Atypical" fibro-osseous lesions: diagnostic challenges and treatment concepts.

The term fibro-osseous lesion is a generic designation of a group of jaw disorders (ranging from inflammatory to neoplastic) that microscopically exhibit, a connective-tissue matrix and islands/trabeculae of bone. Although the histologic appearance, and frequently the clinical and radiographic features, may be similar for many of these lesions, they demonstrate a wide range of biologic behavior. Treatment therefore is varied, and there are few well-established guidelines to help the surgeon. Five fibro-osseous lesions with atypical features are presented to demonstrate the diagnostic difficulties associated with these lesions and to show the need for accurate classification in order to help direct treatment and predict outcome. Final diagnoses for "atypical" fibro-osseous lesions included: multiple ossifying fibromas, unclassifiable fibro-osseous lesion, osteosarcoma with concomitant multiple ossifying fibromas, juvenile or psammomatoid ossifying fibroma, and central low-grade osteosarcoma. "Fibro-osseous lesion" should be viewed as a working diagnosis, and a definitive diagnosis should be actively sought; the addition of "atypical" to this designation suggests the likelihood of an aggressive lesion. Treatment of lesions having atypical and nonclassical microscopic features must be based on the biologic behavior of the tumor.