Low-Grade Myxofibrosarcoma of the Leg Presenting as a Pathological Pilon Fracture: A Case Report

Myxofibrosarcoma (MFS) is among the most common soft-tissue sarcomas of the extremities in elderly patients; however, presentation as a pathological fracture is exceptionally rare. The tumor's fluid-rich myxoid matrix produces magnetic resonance imaging signal characteristics that closely mimic benign vascular lesions, creating a significant diagnostic challenge when encountered outside a tertiary setting. We report a case of low-grade myxofibrosarcoma presenting as a pathological pilon fracture.

A 60-year-old male presented with a 2-week history of ankle pain following an inversion injury that was refractory to conservative management, accompanied by a 6 kg weight loss over 4 months. Examination revealed cachexia, diffuse lower-limb swelling, and skin induration. Plain radiographs demonstrated a sagittally angulated pathological pilon fracture with diffuse moth-eaten osteolysis of the tibia and fibula. Magnetic resonance imaging revealed a large 35 × 6.5 × 6.1 cm inter- and intramuscular lesion initially reported as cavernous lymphangioma. Open core needle biopsy established the diagnosis of low-grade myxofibrosarcoma. The patient declined the recommended high transfemoral amputation; 3 weeks later, cutaneous fungation developed. Final histopathology of the amputation specimen confirmed progression to high-grade myxofibrosarcoma (350 mm) with multifocal bone invasion and clear resection margins. At 48 months postoperatively, the patient remains disease-free.

MFS may present as a pathological fracture with imaging features indistinguishable from benign pathology. Mandatory pre-operative tissue biopsy and prompt referral to a specialist sarcoma center are essential to prevent diagnostic delay, unplanned excision, and the associated risk of tumor progression.