Clear-cell papillary renal cell carcinoma: 24 cases of a distinct low-grade renal tumour and a comparative genomic hybridization array study of seven cases

Adam J, Couturier J, Molinié V, Vieillefond A & Sibony M (2011) Histopathology58, 1064–1071 Clear‐cell papillary renal cell carcinoma: 24 cases of a distinct low‐grade renal tumour and a comparative genomic hybridization array study of seven cases Aims: To report clinicopathological and genomic characteristics of (ccpRCC), a rare, recently characterized renal tumour entity. Methods and results: Twenty‐four renal tumours identified as ccpRCC were collected. Data from comparative genomic hybridization on microarrays (array‐CGH) were obtained for seven of these. Most tumours (58%) occurred in the absence of renal disease. Mean patient age was 58.1 years. Tumours were small (mean size: 2.4 cm) and classified as pT1. Histological characteristics consisted of tubules and papillae lined by a single layer of small clear cells harbouring low‐grade nuclei (Fuhrman grades 1 or 2). Architectural variations, with compact areas (41% of cases) and a micro‐ or macrocystic pattern (67% of cases) were observed frequently. Immunostaining demonstrated diffuse, strong expression of cytokeratin 7 and vimentin, whereas CD10, racemase, RCC antigen, translocation factor E3, TFE3 and translocation factor EB were consistently negative. In seven tumours, array‐CGH detected no chromosomal imbalances. Conclusions: Clear‐cell papillary renal cell carcinoma (ccpRCC) were differentiated from other renal neoplasms by a specific constellation of histopathological and immunohistochemical features, without characteristic genomic imbalances. Clinical, histopathological and genomic data suggested that these tumours have a low potential for malignancy.