EXOPHYTIC VARIANT OF FIBROUS DYSPLASIA (FIBROUS DYSPLASIA PROTUBERANS)

Two cases of an exophytic variant of fibrous dysplasia (fibrous dyspla sia protuberans) are reported in which the lesions protruded far beyon d the normal bone contour mimicking surface lesions of bone. The first case was an 18-year-old man who had a pedunculated calcified mass of the sixth rib in association with radiologically diagnosed fibrous dys plasia of the skull. The second case was a 33-year-old man who had an exophytic lesion of the proximal tibia. Both of these patients were sh own to have benign fibro-osseous lesions consistent with fibrous dyspl asia. The intramedullary portions of the host bone adjacent to the exo phytic masses also were involved by the fibro-osseous lesions and this fact suggests: that the lesions may arise eccentrically in the medull ary spaces and mainly grow outwards. It is important to be aware that fibrous dysplasia occasionally presents as an excrescence on the surfa ce of bone. Careful radiographic and histological correlation is requi red to make a correct diagnosis of this rare variant of fibrous dyspla sia. (C) 1994 by W.B. Saunders Company