Abstract

Primary retroperitoneal tumors are reported to account for 0.2% of all malignancies. Furthermore, 10-20% of all primary retroperitoneal tumors are liposarcomas. Up to 1989, 213 cases of retroperitoneal liposarcoma have been reported in the Japanese literature to our knowledge. Mixed type liposarcomas were rare, and composed 13.8% of all retroperitoneal liposarcomas in this series. We described here a case of retroperitoneal mixed type liposarcoma. A 50-year-old man was admitted to our department with a mass in the left abdomen. Computed tomography and aortography revealed a huge and hypovascular tumor in the retroperitoneal cavity, not containing fat tissue. It was diagnosed as a retroperitoneal tumor and treated surgically. The tumor and the left kidney were encapsulated and could be removed en bloc. The size and weight of the tumor were 28 x 18 x 12 cm and 3,100 g, respectively. Histological examination of the mass proved it to be a mixed type liposarcoma. He was administered OK-432 as adjuvant therapy. After 11 months, bone metastasis to the vertebra appeared. Moreover, lung metastasis also occurred and he died of the disease 15 months after the operation.