Clear cell papillary renal cell carcinoma (CCP-RCC) has recently been recognized as a distinct subtype of renal cell carcinoma (RCC) due to its unique morphologic, immunohistochemical, and genetic features and indolent clinical behavior. However, the incidence of this tumor in a nephrectomy series for renal mass has not been fully investigated. Twelve cases of CCP-RCC were identified from a total of 290 consecutive partial (n = 137) or radical nephrectomies (n = 153) for RCC from 2010 to 2012 in our hospital. In this series, CCP-RCC was the fourth most common (4.1%) kidney tumor following clear cell (conventional) (70%), papillary (16.6%), and chromophobe (5.9%) RCCs. The average age of the CCP-RCC patients was 58.2 years (range, 18-81 years), with an equal sex distribution. Four cases (33.3%) were associated with end-stage renal disease. Of the 12 CCP-RCCs, 9 presented as solitary tumors; 2 coexisted with clear cell RCC; and 1 with papillary RCC. The average size of tumors was 2.5 cm (range, 0.8-6.0 cm). All tumors were pT1 (10 pT1a and 2 pT1b). Two cases were initially misclassified as clear cell RCC. Strong positive cytokeratin 7 stain and negative stains with α-methylacyl-CoA racemase and RCC marker differentiate CCP-RCC from low-grade clear cell RCC with similar histologic features. We conclude that CCP-RCC is a common renal neoplastic entity, representing the fourth most common (4.1%) RCC. It can be easily misclassified due to its overlapping features with low-grade clear cell RCC. In equivocal cases, immunohistochemical stains with a small panel of markers (cytokeratin 7, α-methylacyl-CoA racemase, RCC marker, or CD10) are warranted in making the correct histologic classification.
Keywords: Clear cell papillary renal cell carcinoma; Incidence; Nephrectomy.
© 2013.