[Two cases of giant retroperitoneal liposarcoma].

The first patient was of a 71-year-old woman who was examined for abdominal protuberance. Computed tomography (CT) and magnetic resonanc e imaging(MRI)revealed a giant tumor almost occupying the entire abdomen. En-bloc resection was performed. The tumor was 30 cm in size and weighed 6,500 g. The histological diagnosis was a well-differentiated liposarcoma. The second patient was a 72-year-old woman who visited our hospital after she had been diagnosed with an abdominal tumor by her family doctor. CT and MRI revealed a massive tumor involving various components. The tumor had invaded the left ureter and descending colon; therefore, we performed tumorectomy, left nephrectomy, and descending colectomy. The histopathological findings indicated a well-differentiated, myxoid, pleomorphic liposarcoma. The tumor recurred 4, 5, and 7 years after the first operation. By the fourth operation, the histological subtype of the tumor had changed to a dedifferentiated type.