Venous invasion in renal vein leiomyosarcoma: case report and review of the literature.

Tumors arising from veins are rare, usually present with nonspecific clinical and imaging findings and almost universally show histology of leiomyosarcoma. This twentieth reported case of primary renal vein leiomyosarcoma demonstrates invasion of the renal vein with endoluminal propagation of tumor into the infrahepatic inferior vena cava (IVC), an unreported manifestation. The combination of CT, ultrasound, and angiographic studies allowed differentiation from renal cell carcinoma by suggesting a tumor arising from the renal vein.