Coexpression of cytokeratins 7 and 20 confirms urothelial carcinoma presenting as an intrarenal tumor

BACKGROUND, The differentiation of epithelial tumors arising in the kidney (urothelial vs. renal cell carcinoma) sometimes can be difficult by clinica l and radiologic studies. Because urothelial and renal epithelium express u nique cytokeratin (CK) 7 and 20 profiles, the authors studied the utility o f these markers to confirm the diagnosis of urothelial carcinomas that pres ent clinically as kidney masses. METHODS. Using commercially available monoclonal antibodies, paraffin secti on immunohistochemistry was used to examine two recent cases of urothelial carcinomas presenting as renal tumors. Tissues were stained for CK7 and CK2 0 and the expression compared between the tumor and benign tissue. RESULTS. Both cases showed solid renal masses that clinically and radiograp hically could have been of renal cell origin, but subsequently were confirm ed histologically to be extensive renal involvement by urothelial carcinoma . The tumors coexpressed both CK7 and CK20, which is the expected profile f or carcinomas of urothelial bur not renal origin. CONCLUSIONS. The results of the current study show that coexpression of CK7 and CK20 is a useful diagnostic aid in the differential diagnosis of epith elial kidney tumors of urothelial cell versus renal cell origin. (C) 1999 A merican Cancer Society.