Malignant Transformation in Monostotic Fibrous Dysplasia

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 (n1⁄4 10), computed tomography (CT) (n1⁄4 5), magnetic resonance (MR) (n1⁄4 4), and bone scintigrams (n1⁄4 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 (n1⁄4 4), humerus (n1⁄4 2), tibia (n1⁄4 3), and ilium (n1⁄4 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 (n1⁄4 5), cortical destruction (n1⁄4 5), obvious soft tissue mass (n1⁄4 1), and mineralization (n1⁄4 2). For the 5 cases without surgery, radiographs and CT identified poorly marginated, osteolytic lesions within or near the area with ‘‘ground-glass’’ opacity (n1⁄4 4), cortical erosion (n1⁄4 4), and mineralization (n1⁄4 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 (n1⁄4 10). Pathology reports revealed osteosarcoma (n1⁄4 7), fibrosarcoma (n1⁄4 2), and malignant fibrous histiocytoma (MFH) (n1⁄4 1). At the end of the study, 1 patient died from tumors, 1 patient was alive with lung metastasis, 1 patient g Cui, PhD, and Huizhen Zhang, MD 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. (Medicine 94(3):e369) Abbreviations: ALP = alkaline phosphatase, AP = adriamycin– cisplatin, CT = computed tomography, FD = fibrous dysplasia, MFH = malignant fibrous histiocytoma, MR = magnetic resonance, STIR = short-tau inversion recovery, TE = echo time, TI = inversion time, TR = repetition time. INTRODUCTION F ibrous dysplasia (FD) is an uncommon bone disease 1 that is characterized by the replacement of normal bone structure with abnormal fibro-osseous connective tissue. FD generally has typical imaging findings. Radiographically, the healthy bone is replaced with a more radiolucent, ‘‘ground-glass’’– appearing pattern, with no visible trabecular pattern. There may be endosteal scalloping of the inner cortex, but the periosteal surface is smooth and nonreactive. FD is generally considered a benign, pediatric disease and usually becomes dormant by adulthood. However, FD lesions have the potential to become malignant over decades. Coley and Stewart described the first identified case of sarcoma arising in FD in 1945. Malignancies in FD can occur in monostotic and polyostotic FD. The frequency of malignant change is increased in the polyostotic form of FD, especially in patients with McCune–Albright syndrome or Mazabraud syndrome. Malignant transformation in monostotic FD has rarely been reported. Therefore, in this study, we report 10 unpublished cases of spontaneous transformation in monostotic FD. We present their characteristic clinical features; radiographic, MRI, and computed tomography (CT) features; treatment modalities; and prognoses. The purpose of this study was to investigate the clinical and imaging features of 10 cases of malignant transformation in monostotic FD. MATERIALS AND METHODS