Malignant degeneration in fibrous dysplasia (presentation of 6 cases and review of the literature).

Malignant degeneration of fibrous dysplasia is rare. It occurs with similar frequency at all ages and in both sexes. It is more frequent in cases of polyostotic than in monostotic fibrous dysplasia. In cases of fibrous dysplasia that do show malignant degeneration it is common to find that a high level of alkaline phosphatase persists in the serum, even in adults. Previous radiotherapeutic treatment appears to me a predisposing factor. Osteosarcoma is the most frequent neoplasm, followed at some distance by fibrosarcoma and chondrosarcoma. The tumour is most often localised in the femur; it is not unusual to find it in the tibia, maxilla and mandible. The treatment and prognosis are the same as those of the involved malignant neoplasm.