Colloidal Iron and Immunohistochemical Staining in Chromophobe Renal Cell Carcinoma and Renal Oncocytoma

Because several features of renal oncocytoma overlap those of other renal neoplasms including chromophobe renal cell carcinoma (cRCC), a subtype of renal cell carcinoma, strict diagnostic criteria for differentiating between them have not been clearly defined. Between 1974 and 2001, nephrectomy was performed in 796 cases diagnosed as renal epithelial neoplasms at our department. The pathological diagnosis was cRCC in 15 of them, renal oncocytoma in eight of them. We performed a retrospective study to determine the utility of peanuts agglutinin (PNA), dolichos biflorus agglutinin (DBA), leu M1 (LM1), colloidal iron staining and CD68 staining, in addition to the conservative HE method, to define the histological criteria for the diagnosis of these tumors. PNA staining, DBA staining, and LM1 staining were similarly positive, and there were no significant differences between renal oncocytoma and cRCC. By contrast, using CD68 staining, the cRCCs had a high positive rate of 80% (12/15), but only one of the eight cases (12.5%) was positive. A high proportion of cRCCs stained positive with the macrophage marker CD68 antibody, suggesting that immunohistostaining for CD68 is helpful in making the differential diagnosis between cRCC and renal oncocytoma