Malignant tumors of the ureteral smooth muscle are rare, and only 14 cases have been reported in the literature to date. An 80-year-old ethnic Chinese man was admitted with chief complaints of general malaise, anorexia, and weight loss. Renal ultrasonography demonstrated left
hydronephrosis. Retrograde pyelograms showed partial obstruction of the left ureter with hydroureteronephrosis.Cytology and biopsies of the lesion suggested a malignant tumor. A left nephroureterectomy with excision of the bladder cuff was performed. The tumor was diagnosed
as a leiomyosarcoma histologically.