Expression of prostate-specific membrane antigen in renal cortical tumors

Prostate-specific membrane antigen is a type II membrane glycoprotein that is expressed in benign and neoplastic prostatic tissue and has been recently shown to be also expressed in the neovasculature of various solid malignant tumors including renal cell carcinoma. Renal cell carcinoma is a heterogeneous group of tumors with distinct morphologic and genetic characteristics and clinical behaviors. We performed immunohistochemical studies on formalin-fixed, paraffin-embedded archival material from 75 nephrectomies, using antibodies 13D6 against prostate-specific membrane antigen and CD31 against endothelial cells. The study included 30 clear cell renal cell carcinomas, and 15 of each of papillary and chromophobe renal cell carcinoma and oncocytoma. The extent and intensity of staining were assessed semiquantitatively. In all cases, immunoreactivity was detected only in the tumor-associated neovasculature and not in tumor cells. Clear cell renal cell carcinoma showed the most diffuse staining pattern, where 24/30 cases or 80% had >50% reactive vessels, followed by chromophobe renal cell carcinoma (9/15; 60%) and oncocytoma (5/15, 33%). No diffuse staining was detected in any of the papillary renal cell carcinomas and only focal staining was detected in 11 cases (11/15; 73%). Staining intensity was the strongest in clear cell renal cell carcinoma (25/30; 83%) followed by chromophobe renal cell carcinoma (9/15; 60%), oncocytoma (8/15, 53%) and papillary renal cell carcinoma (5/15; 33%). In summary, prostate-specific membrane antigen is expressed in tumor-associated neovasculature of the majority of renal cortical tumors and is most diffusely and intensely expressed in clear cell renal cell carcinoma and least in papillary renal cell carcinoma. The differences in the expression of prostate-specific membrane antigen in renal cell carcinoma subtypes provide further evidence of the biological diversity of these tumors, and diagnostic and therapeutic applications of such expression can be expanded to include subtypes of renal cell carcinoma.