[A case of retroperitoneal dedifferentiated liposarcoma with tumor thrombus in the inferior vena cava].

We experienced a case of retroperitoneal dedifferentiated liposarcoma with tumor thrombus in the inferior vena cava. A 45-year-old man was pointed out a retroperitoneal mass on ultrasound examination. He was referred to the Department of Urology, Tochigi Cancer Center for critical evaluation. Image diagnostic procedures showed a retroperitoneal mass surrounded by loose tissue and large thrombus in the inferior vena cava. The tumor was removed surgically with right lobe of the liver and segment of the inferior vena cava. Histological examination revealed the tumor composed of the peripheral well differentiated liposarcoma and the central dedifferentiated liposarcoma. Characteristic radiological findings of retroperitoneal liposarcoma with dedifferentiation could be pointed out.