Morphologic, Immunohistochemical and Molecular Analyses of a Huge Clear Cell Papillary Renal Cell Carcinoma

Abstract

Among the tumors of the kidney, the clear cell papillary renal cell carcinoma (CCPRCC) is a recently described entity. This tumor is well circumscribed, with a fibrous capsule, showing mostly a prominent cystic component and a diameter less than 4 cm. Necrosis is not a feature. Tumor cells are clear with low grade nuclei with a predominantly tubule-papillary architecture and immunohistochemical staining strongly positive for CK7, and for CA IX and negative for RACEMASE, features which differentiate this tumor from clear cell renal cell carcinoma (CCRCC) and papillary renal cell carcinoma (papillary RCC). In these latter tumors, it has been reported, unlike the other two, no loss or gain of chromosomes 7 and Y, no chromosome 3p deletion, and no KRAS mutation. In this report, a huge clear cell papillary renal cell carcinoma case, 9 cm diameter, in a 42-year-old male is described. Pathologic diagnosis of the tumor was confirmed by immunohistochemical analysis including CD10, CA IX, CK7, RACEMASE, and 34 beta E12 stainings. Molecular detection of KRAS, BRAF, NRAS, PIK3CA, ALK, ERBB2, DDR2, MAP2K1, RET, and EGFR gene mutational analysis has also been performed. Molecular findings are in accordance with the speculation that the CCRCC is an indolent tumor which may be defined as low malignant potential. In fact, in the molecular analysis, none out of all genes evaluated showed mutation.