[A case of retroperitoneal well-differentiated liposarcoma with metaplastic bone formation].

A 43-year-old female was referred to our hospital from a local doctor. Her chief complaints were weight gain and abdominal fullness. Computed tomography and magnetic resonance imaging showed a huge tumor in the right retroperitoneal space, which adhered to the right kidney. It was resected with concomitant resection of the right kidney. It measured 30×15 cm and weighed 3.0 kg. Histological examination revealed well differentiated liposarcoma with metaplastic bone formation. She has survived 22 months since the operation with no evidence of recurrence. A retoroperitoneal liposarcoma with metaplastic bone formation is rare. Twenty cases have been reported in Japan including our case.