Expression of parafibromin in clear cell papillary renal cell carcinoma

Clear cell papillary renal cell carcinoma (CCPRCC) is a low-grade renal cell neoplasm. In this study, we investigated the expression of parafibromin, CK7, and RCC marker (RCC-Ma) in this tumor by immunohistochemistry in a group of CCPRCC. Twenty cases of CCPRCC were stained for parafibromin and showed diffuse and strong nuclear positivity for this marker. In addition the cases of CCPRCC were stained for CK7 and RCC-Ma, respectively, and the majority of tumors were positive for cytoplasmic staining of CK7 and negative for RCC-Ma. This unique staining pattern can be useful in the differential diagnosis from conventional clear cell renal cell carcinomas, which have a higher positivity rate for RCC-Ma, but largely negative for CK7 and parafibromin, and papillary renal cell carcinomas, which are usually positive for CK7 and RCC-Ma but are largely negative for parafibromin.