This report concerns a 67-year-old male with malignant fibrous histiocytoma arising from the psoas muscle and perirenal soft tissue. The tumor was considered a mesenchymal neoplasm. These are generally clinically and radiologically indistinguishable from other retroperitoneal tumors. This patient received en bloc resection of the retroperitoneal tumor and radical nephrectomy without adjuvant therapy. He underwent excision of a retroperitoneal cystic mass complicated with lymph leakage one year postoperatively. Discharged in a stable condition after one week of total parenteral nutrition, the patient remains disease-free 16 months postoperatively. Zhonghua Yi Xue Za Zhi (Taipei). 1998 Feb;61(2):104-9(8):