Primary leiomyosarcoma of the inferior vena cava presenting as a renal mass

Leiomyosarcoma of the inferior vena cava (IVC) is an extremely rare entity. We present the case of a 62-year-old woman who was found to have a large right upper quadrant mass upon examination by her primary care physician in evaluation for diffuse abdominal pain accompanied by anorexia and weight loss. A computed tomographic scan and magnetic resonance imaging demonstrated a 13-cm retroperitoneal lesion that appeared to stem from the right kidney and yielded a tumor thrombus up to the level of the hepatic venous confluence. The patient underwent a right radical nephrectomy and IVC thrombectomy for treatment of a presumed renal cell carcinoma. Instead, pathology revealed the tumor to be a leiomyosarcoma of the IVC. We document this unusual presentation of an extremely rare tumor entity.