A Case of Retroperitoneal Well-Differentiated Liposarcoma with Metaplastic Bone Formation

Abstract

A 68-year-old man admitted for abdominal fullness was found in Computed tomography (CT) and magnetic resonance imaging (MRI) to have a homogeneously enhanced right retroperitoneal tumor with focal calcification adjacent to right kidney and right psoas muscle. Abdominal ultrasound showed a tumor with calcification dominant in the center of highly echoic parts. Angiograpy of the right renal artery and right lumbar artery showed tumor staining. We resected the tumor. The 24.5×20.5×11.5cm tumor adhered to the inferior pole of the right kidney and weighed 1, 600g. Histological examination showed mature adipose tissue with collagen fiber, including trabecular bone tissue. The definitive diagnosis was primary well-differentiated liposarcoma with metaplastic bone formation. The postoperative course was uneventful and the patient has survived 15 months since surgery with no evidence of recurrence.