A 62-year-old otherwise healthy woman presented with three to four months of mechanical right groin pain radiating to the right buttock. She had a history of a benign soft-tissue mass in the right thigh that had been biopsied 10 years earlier, and the patient was told it was a myxoma. No other workup was done at the time, and no other lesions were clinically detectable. She had been very active and played tennis regularly. She was assessed with a hip ultrasound for her right groin pain and was prescribed physiotherapy. During physiotherapy, she felt a snap in her right groin and was no longer able to ambulate without a walker. Initial radiographs demonstrated a lucent intramedullary lesion within the subtrochanteric region:further characterized by a focally aggressive appearance with cortical destruction and lytic expansion of the lesser trochanter (Figures 1(a) and 1(b)). A ground-glass appearance, typical of fibrous dysplasia, was also noted in the mid-femoral shaft (Figure 1(c)).
Further workup included a Computed Tomography (CT) scan of the chest, abdomen, and pelvis which showed multiple hepatic and renal cysts but no evidence of a primary carcinoma or lung metastases. Bloodwork including serum protein electrophoresis was normal. A Total Body Bone Scan (TBBS) revealed increased uptake in the right proximal femur and two areas of relatively mild uptake in the mid femur. Fat-suppressed T2 Magnetic Resonance Imaging (MRI) displayed an intermediate to high signal lesion within the medullary cavity of the proximal and mid right femoral shaft (Figure 2(a)). In line with the initial radiographs in which two benign sites of fibrous dysplasia were noted, in the third proximal lesion, there was cortical destruction with an extraosseous soft-tissue mass in the region of the lesser trochanter. Additionally, in keeping with the known myxoma, a soft-tissue T2 hyperintense mass within the medial distal thigh was also present (Figure 2(b)). On further review of the MRI images, five other myxomas were seen. The imaging features were consistent with Mazabraud's Syndrome, with sarcomatous transformation of benign fibrous dysplasia in the proximal femur.
Due to the high risk of fracture, the patient was immediately placed on bedrest and a biopsy was not performed:as a preventative measure to reduce fracture risk. She was taken to the operating room and underwent wide resection of the proximal right femur with endoprosthetic reconstruction via a lateral approach. Along with bony specimens, one of the soft-tissue masses was also excised and sent to pathology for investigation (Figures 3(a) and 3(b)). Pathology later confirmed a high-grade osteosarcoma in the setting of fibrous dysplasia and a benign myxoma (Figures 4(a)-4(d)). There were no complications during the procedure.
Postoperatively, the patient stayed in the hospital for one week, with physiotherapy beginning on postoperative day one. Her postoperative course followed the normal trajectory of recovery with no major complaints or issues at her two-week follow-up. The patient declined adjuvant chemotherapy. The standard management of osteosarcoma at our center would include wide surgical excision with neoadjuvant or adjuvant chemotherapy (methotrexate- and doxorubicin-based multidrug regimens). The patient is being followed to assess for complications and local or systemic relapse every three months with radiographs of the femur and chest. At one year postoperatively, there have been no complications or evidence of disease relapse.