Expression of vitamin D receptor in clear cell papillary renal cell carcinoma.

Clear cell papillary renal cell carcinoma (ccpRCC) is a recently recognized subtype of renal cell carcinoma. In this study, we investigated the clinicopathological and immunohistochemical features in a group of 26 cases of ccpRCC, with a special emphasis on the expression of vitamin D receptor (VDR). The mean age of patients was 53.3 years (range 36-74 years), and the mean tumor size was 2.5 cm (range 0.5 to 6.5 cm). During follow-up (range 12-121 months, median 50 months), no recurrence or metastasis was observed. Histopathologically, all cases of ccpRCC exhibited a tubular and papillary architecture, covered by tumor cells with clear cytoplasm. Immunohistochemistry showed intermediate (5/26, 19%) to diffuse (21/26, 81%) and moderate (2/26, 8%) to strong (24/26, 92%) membranous staining for VDR in each case. All cases (26/26, 100%) were diffuse and strong cytoplasmic and fibrillar staining for cytokeratin 7 (CK7), but negative forα-methylacyl-CoA-racemase (AMACR). Each case showed diffuse (26/26, 100%) and moderate (4/26, 15%) to strong (22/26, 85%) membranous staining for carbonic anhydrase IX (CA IX). In addition, the majority of cases showed negative for cluster of differentiation 10 (CD10) (20/26, 77%) and renal cell carcinoma maker (RCC-Ma) (24/26, 92%). This unique staining pattern is helpful for distinguishing ccpRCC from its mimics. Furthermore, VDR positive expression suggests that ccpRCC originates from the precursor epithelium of distal nephron.