The utility of epithelial membrane antigen and vimentin in the diagnosis of chromophobe renal cell carcinoma.

We evaluated the immunohistochemical expression of epithelial membrane antigen (EMA) and vimentin (VMT) in chromophobe renal cell carcinoma (CHRCC). We also studied the utility of EMA and VMT immunostains in helping differentiate CHRCC from renal oncocytoma and conventional (clear cell) renal cell carcinoma with granular morphology (GCRCC). Immunohistochemical staining for EMA and VMT was performed on 21 cases of CHRCC, 16 cases of renal oncocytoma, and 28 cases of GCRCC. The diagnosis in all cases was by concurrence of all pathologists involved in the study and was based entirely on examination of routinely stained slides. All cases were classic examples of these tumor types and presented no diagnostic difficulties. The intensity of immunohistochemical staining was graded on a scale of 0 to 3 (0 = no staining; 1 = equivocal; 2 = unequivocal, moderate intensity; and 3 = unequivocal, high intensity). Positive immunohistochemical staining was defined as unequivocal staining of at least 20% of the neoplastic cells. All cases of CHRCC were positive for EMA and negative for VMT. The same immunophenotype was observed in 75% of renal oncocytoma and 21% of GCRCC. In summary, all CHRCC cases in our study demonstrated immunohistochemical staining for EMA and not VMT. However, we also found that the same immunophenotype is observed in 75% of renal oncocytoma and in 21% of GCRCC, precluding its utility for positive identification of CHRCC. Nevertheless, the lack of such an immunophenotype is a reliable indication that a neoplasm under consideration is not CHRCC.