Renal vein leiomyosarcoma: imaging and clinical features of a renal cell carcinoma mimic.

Renal vein leiomyosarcoma is a rare tumor whose clinical and imaging features can significantly overlap with those of advanced primary renal neoplasms, particularly renal cell carcinoma. IRB approval was obtained for a retrospective review of clinical and imaging information for five patients with the pathologically proven diagnosis of renal vein leiomyosarcoma at two institutions. Among the five patients, two were female and three male; average age 58.6 (range 42-77). Three patients presented with flank or abdominal pain, one with pulmonary embolism, and one with weight loss and fatigue. Mass size ranged from 4 to 10 cm. Four masses were left-sided and one right-sided. Tumors involved and expanded the renal vein in all cases, with tumor extension to the renal hilum in one case, through the renal hilum into renal parenchyma in two cases, and into inferior vena cava in two cases. All masses demonstrated contrast enhancement, which was solely peripheral in one case. In all cases, extrarenal tumor volume was greater than renal parenchymal tumor volume. When renal masses are predominantly or exclusively intravascular, consideration should be given to the diagnosis of renal vein leiomyosarcoma because preoperative biopsy results could significantly alter management.