Renal oncocytoma: report of two cases.

The clinico-radiologic, gross, microscopic and ultrastructural findings in 2 cases of renal oncocytoma are reported. The diagnosis of renal oncocytoma has important clinical and prognostic implications, since the neoplasia is usually benign despite its often large size. The differential diagnosis with other renal neoplasms, in particular renal cell carcinoma, is discussed. The problem of the pre-operatory diagnosis of renal oncocytoma is explored on the basis of clinico-radiologic findings and/or histologic examination of pre- or intraoperatory biopsy. In view of the tumor's benign nature, this diagnosis implies tumorectomy, but its close resemblance to renal cell carcinoma at present counsels nephrectomy. A final diagnosis of oncocytoma may be formulated only after histologic examination of several specimens and ultrastructural confirmation.