Renal oncocytoma: review of literature and report of six cases.

6 cases of renal oncocytomas are described. Preoperative diagnosis is difficult in spite of new clinical diagnostic methods. In our series oncocytoma was diagnosed angiographically in 1 case and in 3 cases carcinoma was suspected. 5 of 6 cases, reevaluated postoperatively, fulfilled three of the four criteria of Ambos et al. for oncocytoma. Ultrasonography is a good exclusion diagnostic method for renal neoplasms. Oncocytoma may be suspected if the tumor projects nearly totally outside the renal contour as we found in 3 of our 6 cases. Aspiration biopsy smears have a diagnostic value in the evaluation of renal neoplasms. Cytologically we preoperatively diagnosed oncocytoma in 1 of 3 cases in which biopsy was performed. We warn, however, about the mosaic pattern of renal neoplasms. Renal cell carcinomas may have large areas composed of oncocytes. Frozen section analysis is a potentially hazardous peroperative diagnostic method in large tumors if oncocytoma is suspected.