CD9 and vimentin distinguish clear cell from chormophobe renal cell carcinoma.

Background: Clear cell renal cell carcinoma (ccRCC) and chromophobe renal cell carcinoma(chRCC) can usually be distinguished by histologic characteristics. Occasionally, diagnosis proveschallenging and diagnostic difficulty will likely increase as needle biopsies of renal lesions becomemore common.Methods: To identify markers that aid in differentiating ccRCC from chRCC, we used geneexpression profiles to identify candidate markers that correlate with histology. 39 antisera andantibodies, including 35 for transcripts identified from gene expression profiling, were evaluated.Promising markers were tested on a tissue microarray (TMA) containing 428 renal neoplasms.Strength of staining of each core on the TMA was formally scored and the distribution of stainingacross different types of renal neoplasms was analyzed.Results: Based on results from initial immunohistochemical staining of multitissue titer arrays, 23of the antisera and antibodies were selected for staining of the TMA. For 7 of these markers,strength of staining of each core on the TMA was formally scored. Vimentin (positive in ccRCC)and CD9 (positive in chRCC) best distinguished ccRCC from chRCC. The combination of vimentinnegativity and CD9 positivity was found to distinguish chRCC from ccRCC with a sensitivity of100.0% and a specificity of 95.2%.Conclusion: Based on gene expression analysis, we identify CD9 and vimentin as candidatemarkers for distinguishing between ccRCC and chRCC. In difficult cases and particularly when theamount of diagnostic tissue is limited, vimentin and CD9 staining could serve as a useful adjunct inthe differential diagnosis of ccRCC and chRCC