Malignant change secondary to fibrous dysplasia.

Background: Malignant change in fibrous dysplasia (FD) is very rare. This study was carried out to establish some characteristic clinical information about this disorder.

Methods: Four cases with a malignant change in FD out of 128 cases with FD were surgically treated and followed up for a median period of 61.3 months. The mean age of the patients was 39.8 years. Clinical features, radiological findings, and the outcome were analyzed for each of the four cases.

Results And Conclusion: The sites of the lesions were tibia (2 cases), femur (1 case), and rib (1 case). The forms of FD were monostotic in one case and polyostotic in three cases. Radiologically, plain films and computed tomography (CT) showed osteolytic lesions with poorly delineated margins within and/or near areas having a ground-glass appearance. In the osteolytic lesions, simple cystic changes associated with old FD could be excluded by enhanced magnetic resonance imaging (MRI). Histopathologically, two cases were osteosarcoma, one case was malignant fibrous histiocytoma (MFH), and one case was fibrosarcoma. The management of this disease should be decided according to the type of primary high-grade bone sarcoma. One patient, with MFH, was dead of lung metastasis 13 months after surgery. The others are alive without disease.