右腸腰筋筋肉内脂肪腫が並存した後腹膜原発脱分化型脂肪肉腫の一例

Abstract

A 63-year-old woman was autopsied who showed a 20cm-sized tumor in the retroperitoneal cavity with progressive anemia. Histologically, undifferentiated tumor cells with eosinophilic cytoplasm were proliferating in a solid pattern. Some well-differentiated lipoma-like cells and lipoblasts were scattered. A necrotic area with hemorrhage was observed in the tumor; however, mitotic figures were found to be rare. In the adjacent skeletal muscle tissue, intramuscular lipoma was observed. In immunohistochemistry, the undifferentiated tumor cells were positive for CDK4 and p16. From these findings, the tumor was diagnosed as dedifferentiated liposarcoma.