Osteofibrous dysplasia-like adamantinoma of bone: a report of five cases with immunohistochemical and ultrastructural studies.

This report describes five cases of osteofibrous dysplasia-like adamantinoma of the tibia in young patients ranging from ages 4 1/2 to 14 years. Radiologically and histologically, these cases were indistinguishable from osteofibrous dysplasia of bone, and no epithelial cells were recognized on routine staining. However, epithelial differentiation was seen in the form of scattered keratin-positive cells in all five cases, and tonofilaments in four cases. The patients were treated by curettage, and three had recurrences. Follow-up showed no progression to classic adamantinoma. Osteofibrous dysplasia-like adamantinoma is a special histological type of adamantinoma that affects children and adolescents. It differs from classic adamantinoma in that it lacks conspicuous nests and masses of epithelial cells, and the prognosis after conservative treatment is generally good. Recent publications suggest that osteofibrous dysplasia-like adamantinoma is a precursor of classic adamantinoma. In a comparative study of three cases of classic adamantinoma, we found, in the fibroblastic stroma of the tumors, spindle epithelial cells that were indistinguishable from the epithelial cells of osteofibrous dysplasia-like adamantinoma. This finding suggests that there is an overlap between these conditions. Four additional cases of osteofibrous dysplasia of the tibia from our files lacked epithelial differentiation. It is most likely that osteofibrous dysplasia is part of the morphologic spectrum of adamantinoma.