Renal sarcoma and sarcomatoid renal cell carcinoma: CT and angiographic features.

Computed tomographic (CT) and angiographic findings in 14 patients (eight men, six women, aged 30-72 years) with sarcomatoid renal cell carcinoma (SRCC) and various types of renal sarcoma are described. There were four patients with SRCC; three, leiomyosarcoma; two, liposarcoma; two, fibrosarcoma; and one each of unclassified renal sarcoma, clear cell sarcoma, and malignant fibrous histiocytoma. The most frequent presenting symptom was an abdominal mass or pain. All 14 patients underwent CT, and 11 underwent selective renal angiography. The diagnosis of renal sarcoma should be suspected when CT findings suggest that the tumor arises from the renal capsule or renal sinus and when the tumor is hypovascular or avascular on angiograms. The characteristic negative attenuation values for liposarcomas permit a specific diagnosis. Sarcomas that originate in the renal parenchyma and SRCC cannot be easily differentiated from renal cell carcinoma; however, renal sarcomas do not appear to have a propensity for extension into the renal vein or the inferior vena cava.