MALIGNANCIES IN FIBROUS DYSPLASIA

Background. Malignancies in fibrous dysplasia are rare. Most cases hav e been published as single case reports. The role of radiation therapy in the occurrence of sarcoma, in fibrous dysplasia is still controver sial. Methods. The Mayo Clinic files were reviewed, including Mayo Cli nic cases and consultation cases, to collect all cases of sarcomas ari sing in fibrous dysplasia. Results. Among 1122 cases with a histologic diagnosis of fibrous dysplasia, 28 cases of sarcoma were found. These 28 cases included 16 Mayo Clinic cases and 12 consultation cases. The sarcomas occurred in 19 cases of monostotic fibrous dysplasia and 9 c ases of polyostotic disease (only 1 of Albright's syndrome). The most common histotype was osteosarcoma (19 cases), followed by fibrosarcoma (5 cases), chondrosarcoma (3 cases), and malignant fibrohistiocytoma (1 case). Of the 28 patients, 13 (46%) had received radiation therapy before the sarcoma developed. Most of these sarcomas occurred in the c raniofacial bones (13 cases) or in the proximal femur (7 cases), follo wed by the humerus, pelvis, tibia, and scapula. Conclusions. Prognosis was poor. Sarcomas may arise with or without radiation. Early diagnos is and adequate treatment may lead to improved prognosis.