[A case of acute progressive primary inflammatory fibrosarcoma of the retroperitoneum].

A 70-year-old man with liver cirrhosis presented to us with abdominal distention. Computed tomography revealed a giant retroperitoneal tumor. Examination of a biopsy specimen led to a diagnosis of primary inflammatory fibrosarcoma of the retroperitoneum. However, disease progression was rapid, and the patient died 6 weeks after the onset of the disease. Autopsy revealed that the tumor arose from the retroperitoneum and infiltrated the omentum and mesentery. Prognosis of inflammatory fibrosarcoma is poor if resection is incomplete. Establishment of treatment for unresectable cases is necessary.