Parvalbumin is constantly expressed in chromophobe renal carcinoma

Chromophobe renal carcinoma is composed of neoplastic cell showing several features similar to those found in the intercalated cells of the collecting ducts. Because the distal nephron expresses calcium-binding proteins playi ng a role in calcium homeostasis, we reasoned that these proteins could be expressed by chromophobe carcinoma and therefore represent a diagnostic mar ker. We studied the immunohistochemical expression of different calcium-bin ding proteins (parvalbumin, calbindin-D28K, and calretinin) in 140 renal tu mors, including 75 conventional (clear cell) carcinomas, 32 chromophobe car cinomas, 17 papillary renal cell carcinomas, and 16 oncocytomas. Parvalbumi n was strongly positive in all primary chromophobe carcinomas and in one pa ncreatic metastasis; it was positive in 11 of 16 oncocytomas and absent in conventional (clear cell) and papillary renal cell carcinomas, either prima ry or metastatic. Calbindin-D28K and calretinin were negative in all tumors , with the exception of two chromophobe carcinomas, four oncocytomas, and t wo papillary renal cell carcinomas showing inconspicuous calretinin express ion. Our data demonstrate that parvalbumin may be a suitable marker for dis tinguishing primary and metastatic chromophobe carcinoma from conventional (clear cell) and papillary renal cell carcinoma. Moreover, they suggest a r elationship between chromophobe renal carcinoma and renal oncocytoma and in dicate that chromophobe carcinoma exhibits differentiation toward the colle cting-duct phenotype.