Dedifferentiated Chondrosarcoma of the Distal Femur: Diagnostic Challenges and Limb Salvage with Double-Barrel Fibular Graft Reconstruction

Dedifferentiated chondrosarcoma (DCS) is a rare and aggressive variant of chondrosarcoma characterized by a biphasic histological pattern and poor prognosis. We report a case of DCS arising in the distal femur of a 48-year-old woman who presented with progressive pain and swelling. Radiographs and magnetic resonance imaging revealed a lytic, destructive lesion with a large soft tissue component and heterogeneous signal characteristics suggestive of an aggressive neoplasm. Initial core biopsy was inconclusive, highlighting the challenges of sampling in heterogeneous tumors. Interval imaging demonstrated rapid progression, raising suspicion for high-grade transformation; however, definitive diagnosis was established only after wide surgical resection. The patient underwent limb salvage surgery with reconstruction using a double-barrel autologous fibular graft. Histopathology confirmed DCS, showing an abrupt transition between a low-grade chondroid component and a high-grade spindle cell sarcoma. Postoperative follow-up at 6 months showed no evidence of recurrence. This case underscores the importance of adequate and targeted tissue sampling in suspected chondrosarcoma, particularly when imaging demonstrates heterogeneity. While imaging plays a critical role in raising suspicion, definitive diagnosis relies on histopathologic evaluation. Early recognition and appropriate surgical management remain essential in optimizing outcomes in this aggressive malignancy.