[1036] Clear Cell Papillary Renal Cell Carcinoma (RCC) Is the 4th Most Common Histologic Type of RCC: A Study of 290 Consecutive Nephrectomies for RCC

Steven Shen, Shaojiang Zheng, Haijun Zhou, Luan Truong, Jae Ro, Alberto Ayala. Methodist Hospital, Houston, TX; Hainan Medical College, Haikou, Hainan, China

Background: Clear cell papillary renal cell carcinoma (CCP-RCC) has recently been recognized as a distinct subtype of RCC due to its unique morphologic, immunohistochemical and genetic features and indolent clinical behavior. There have been a number of case series of sporadic or end-stage renal disease (ESRD) associated-CCP-RCC, but the incidence of this tumor has not been reported.
Design: A total of 290 consecutive partial (n=137) or radical nephrectomies (n=153) for RCC from 2010-2012 in our hospital were reviewed. The following clinicopathologic features were studied: age and sex, tumor size, histologic subtype, Fuhrman nuclear grade, pathologic stage, associated ESRD. The diagnosis of CCP-RCC was based on the typical morphologic features and confirmed by immunohistochemistry (CK7 strongly positive, AMACR and RCC marker negative).
Results: Among the 290 RCCs, twelve (4.1%) cases of CCP-RCC were identified. Clear cell (conventional), papillary, chromophobe, and unclassified RCC accounted for 70%, 16.6%, 5.9%, and 1.7%, respectively. The remaining five (1.7%) tumors were tubulocytic, mucinous tubular and spindle cell, Xp11 translocation and ESRD-associated RCC. Of the 12 CCP-RCCs, nine presented as solitary tumors and 2 coexisted with a clear cell RCC and papillary RCC. Four cases (33.3%) were associated with ESRD. The average patients' age was 58.2 years (range 17.8-80.6) with an equal gender distribution. The average size of tumors was 2.5 cm (range 0.8 cm to 6.0 cm). All tumors were of pT1 tumors (10 pT1a and 2 pT1b). Two cases were initially classified as clear cell RCC. The youngest patient was a 17.8 year old boy with VHL disease and also had multiple clear cell RCCs.
Conclusions: In this study, we have shown that CCP-RCC is the fourth most common histologic subtype of RCC in the current series. It can be easily misclassified as clear cell RCC. Although it is frequently associated with ESRD and may coexist with other types of RCC, it occurs more often as a solitary renal mass. Immunohistochemical stains with a small panel of markers are helpful in making the correct histologic classification.
Category: Genitourinary (including renal tumors)

Tuesday, March 5, 2013 1:00 PM

Poster Session IV # 193, Tuesday Afternoon


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