Retroperitoneal mixed-type liposarcoma showing features of four different subtypes.

Mixed-type liposarcoma is a rare soft tissue tumor. This report describes a 50-year-old man with retroperitoneal mixed-type liposarcoma that consisted of four pathologically different components. Preoperative CT and MRI showed a giant retroperitoneal mass composed of several nodules with various attenuation and signal intensity. At laparotomy, the tumor appeared to be composed of four components. Pathologic examination revealed that each component was of a histologically different subtype. Mixed-type liposarcoma containing four different subtypes is extremely rare. Its clinical and pathologic features are briefly reviewed.