Dedifferentiated liposarcoma (DDL), exhibiting divergent heterologous differentiation, is a rare entity with a variable reported incidence. These tumors typically arise in the retroperitoneum, often attaining substantial size and presenting at advanced stages, thereby posing significant diagnostic and therapeutic challenges. We report a rare case of recurrent DDL with dual heterologous differentiation—osteosarcomatous and chondrosarcomatous—in an elderly male initially presenting with symptoms mimicking an inguinal hernia. Contrast-enhanced CT revealed a massive abdominal mass occupying the left retroperitoneal space, with obliteration of fat planes adjacent to the left kidney and spleen. Exploratory laparotomy identified a large tumor displacing the left and transverse colon along with the mesocolon and ureter across the midline. The mass was surgically excised while preserving the left kidney. Gross examination revealed multiple tumor fragments, ranging from 15 to 40 cm in size, with a cumulative weight exceeding 25 kg. Extensive histopathological sampling revealed a well-differentiated liposarcoma with areas of heterologous differentiation, exhibiting features of both chondrosarcoma and osteosarcoma. A final diagnosis of recurrent multifocal giant retroperitoneal DDL with dual heterologous differentiation was established. Despite the tumor’s multifocality and recurrence, comprehensive radiological assessment, meticulous surgical excision, and detailed pathological evaluation were critical in achieving an accurate diagnosis.
