Caveolin-1 immunohistochemical analysis in differentiating chromophobe renal cell carcinoma from renal oncocytoma.

Chromophobe renal cell carcinoma (ChRCC) and oncocytoma might mimic each other histologically. We studied the immunohistochemical staining pattern of caveolin-1 in 21 ChRCCs and 26 oncocytomas and compared it with cytokeratin (CK) 7 to evaluate its usefulness in differentiating these 2 neoplasms. All 21 ChRCCs (100%) were positive for caveolin-1, 20 of which were stained in 20% or more of the tumor cells. In contrast, only 3 (12%) of 26 oncocytomas showed positivity in fewer than 20% tumor cells and 23 (88%) of 26 were negative. In the nonneoplastic kidney, positive caveolin-1 staining was detected in the interstitial blood vessels and the parietal cells of the Bowman capsules but not in the tubular epithelium and glomerular and peritubular capillaries. All 21 ChRCCs (100%) were positive for CK7, with 18 (86%) stained in 20% or more of the tumor cells and 3 (14%) in fewer than 20%. Of 26 oncocytomas, 25 (96%) were positive for CK7, with 7 (27%) stained in 20% or more of the tumor cells and 18 (69%) in fewer than 20%. These results strongly suggest that caveolin-1 immunohistochemical analysis is useful for differentiating ChRCC from oncocytoma and is superior to CK7.