Primary retroperitoneal plasmacytoma with tumor thrombus within the renal vein

A case of primary retroperitoneal plasmacytoma causing a tumor thrombus within the renal vein is described. The use of radiographic techniques, including ultrasonography, computerized tomography and angiography, facilitated an accurate diagnosis. Tumor thrombi within the renal vein are rare except in cases of primary renal or adrenal neoplasms. In a patient with radiological evidence of retroperitoneal tumor and tumor thrombus within the renal vein plasmacytoma should be considered in the differential diagnosis of retroperitoneal neoplasms.