Renal oncocytoma: a rare renal tumor with typical angiographic features

We report on a case of renal oncocytoma (proximal tubular adenoma) with typical vascular architecture. The vascular supply of the oncocytoma showed a 'spoke-wheel'-like pattern. The typical angiographic features may help to differentiate oncocytomas from hypernephromas and thus diagnose it as such in the preoperative period. By the use of the electron microscope some typical invasions into a small vein could be traced, therefore it seems likely that renal oncocytoma is semi-malignant. Confusion of the renal oncocytoma with a large renal cyst is a classical diagnostic error which can be fatal.