[Malignant fibrous histiocytoma of perirenal tissue: a case report]

A 75-year-old woman was admitted to our hospital with an extremely large retroperitoneal tumor that had been detected with ultrasound on a routine health check. She had no complaint except lumbar pain. Computed tomography revealed a heterogenous tumor located outside the right kidney which was enhanced gradually. Doppler ultrasound showed mild vascularity in the tumor. We performed tumorectomy and right nephrectomy because the tumor was adherent to the right kidney. The tumor was 16 x 11 x 7 cm in size and weighed 621 g. The histopathological diagnosis was malignant fibrous histiocytoma. The tumor was considered to have arisen from perirenal tissue.