Primary pelvic retroperitoneal malignant fibrous histiocytoma in a female with high-grade recurrence

Myxofibrosarcoma or malignant fibrous histiocytoma (MFH) is the most common soft tissue sarcoma. However, primary pelvic and retroperitoneal myxoid is an extremely rare tumor. We report a case of a 49-year-old woman diagnosed with primary MFH originating from the left gluteal muscle and presenting with a large pelvic mass. A 49-year-old woman G0 presented with a 3-year history of progressive left leg sciatica pain, left lower extremity edema, and a pelvic mass consistent with low-grade malignant fibrous histiocytoma upon surgical resection. Despite adjuvant radiotherapy (RT), she developed recurrence underwent within 7 months. She underwent repeat surgical resection with histopathology showing a MFH with high-grade features. We describe this case and review the literature of MFH. MFH of the pelvis and retroperitoneum is extremely rare. It has a high mortality rate and short overall survival. The tumor is characterized by local invasion, while lymph node or vascular metastases are uncommon. Complete tumor resection is the best primary treatment and is usually followed by adjuvant RT or chemotherapy. These patients must have close observation for local recurrence.