Fibrous dysplasia with locally aggressive malignant change.

This is a case report of a tumour which showed all the histological features of fibrous dysplasia without any features of high-grade malignancy, yet had become locally aggressive, causing cortical erosion and extension into soft tissue. Fibrous dysplasia is a well-recognised entity that encompasses monostotic lesions, polyostotic involvement and Albright's syndrome [6, 8]. Lesions in bone usually spare the epiphysis before puberty, but often involve the epiphyseal area after maturity and can progress during adult life [3]. Unless cystic [6, 10] or malignant change [7, 10, 11] occurs, fibrous dysplasia usually remains contained within bone.