Immunocytochemical analysis of band 3 protein in renal cell carcinoma, nephroblastoma, and oncocytoma.

Band 3 protein is an anion-exchange protein that in the human kidney is restricted to a subpopulation of collecting duct-intercalated cells; however, it is absent in the metanephric-derived cells of the nephron. We have studied band 3 protein expression in a series of 60 renal tumors that included 10 oncocytomas, 42 renal cell carcinomas, and eight nephroblastomas by using frozen tumors and a monoclonal antibody. We detected band 3 protein expression in nine of 10 oncocytomas but not in any renal cell carcinomas or nephroblastomas. This finding confirms that band 3 protein is a specific marker for oncocytoma and therefore may have a potential diagnostic application. It also supports the contention that renal cell carcinoma and oncocytoma are histogenically unrelated; the former is metanephric blastema derived and the latter is ampullary bud derived.