RESUMEN
A dedifferentiated liposarcoma of the retroperitoneum is an extremely rare tumor. A 51-year old man was admitted to our department because a retroperitoneal mass was seen on abdominal computed tomography at another hospital. Computed tomography of the abdomen and magnetic resonance imaging showed a large pelvic mass located in the right hemipelvis, and it was pushing the right ureter and invading the right kidney, duodenum, colon and inferior vena cava. The patient underwent right radical nephrectomy, pylorus preserving pancreatoduodenectomy, right hemicolectomy and artificial blood vessel replacement for the inferior vena cava. The histopathological diagnosis was dedifferentiated liposarcoma and the patient was free from recurrence on the computed tomography that was done 6 months after the operation.