Malignant Transformation in Monostotic Fibrous Dysplasia: Clinical Features, Imaging Features, Outcomes in 10 Patients, and Review

Malignant transformation in fibrous dysplasia (FD) is uncommon. The purpose of this study was to investigate clinical and imaging features, and outcomes of malignant transformation in monostotic FD. Data for 10 pathologically confirmed malignant transformations in monostotic FD from January 2005 to December 2013 were retrospectively reviewed. Patient data were recorded, and radiographs (n = 10), computed tomography (CT) (n = 5), magnetic resonance (MR) (n = 4), and bone scintigrams (n = 10) were evaluated for lesion location, margin, cortical destruction, marrow involvement, periosteal reaction, and soft tissue mass by 2 musculoskeletal radiologists with agreement by consensus. Clinical features, management, and prognosis were also analyzed for each of the 10 cases. There were 8 male and 2 female patients (mean age 46.5 ± 15.9 years). The affected sites were the femur (n = 4), humerus (n = 2), tibia (n = 3), and ilium (n = 1). Five cases had received previous surgery and 5 cases had no history of surgery. No patients had been given prior irradiation treatment. For the 5 cases with surgery, radiographs and CT showed purely osteolytic lesions with poor margination in the curettage area (n = 5), cortical destruction (n = 5), obvious soft tissue mass (n = 1), and mineralization (n = 2). For the 5 cases without surgery, radiographs and CT identified poorly marginated, osteolytic lesions within or near the area with “ground-glass” opacity (n = 4), cortical erosion (n = 4), and mineralization (n = 2). Magnetic resonance imaging (MRI) also identified lesions with heterogeneous signal intensity and pronounced enhancement. Bone scintigraphy revealed eccentric increased uptake of radionuclide in monostotic lesion (n = 10). Pathology reports revealed osteosarcoma (n = 7), fibrosarcoma (n = 2), and malignant fibrous histiocytoma (MFH) (n = 1). At the end of the study, 1 patient died from tumors, 1 patient was alive with lung metastasis, 1 patient experienced recurrence, and 7 patients were alive without recurrence. Patients with FD and a history of surgery should be followed up, for the osteolytic lesions in the operative areas strongly indicate the malignant transformation. The radiographic feature of FD-related malignancies is poorly marginated, mineralized, and osteolytic lesions with cortical destruction. Further investigations are needed to explore the pathogenesis of malignancies in FD and to establish optimal therapeutic strategies.