[880] Frequency of Clear Cell Papillary Renal Cell Carcinoma in Cases of Low Grade Clear Cell Renal Cell Carcinoma: A 12 Year Retrospective Study from a Single Cancer Center

Simpal Gill, Sirisa Kandel, Bo Xu. State University of New York at Buffalo, Buffalo, NY; Roswell Park Cancer Institute, Buffalo, NY

Background: Clear cell papillary renal cell carcinoma (CCPRCC) is a recently recognized entity after 2004 World Health Organization classification of renal tumors. CCPRCC has unique histomorphological, genetic and immunohistochemical characteristics. The distinction of CCPRCC from clear cell and papillary RCC is crucial because the former has a favorable clinical outcome based on current data. CCPRCC may be interpreted in the past as other renal cell carcinomas, particularly low grade clear cell or papillary renal cell carcinoma (RCC). In this study, the frequency of CCPRCC in previously diagnosed low grade and low stage clear cell RCC was examined.
Design: Cases with previously diagnosed low grade clear cell RCC, (Fuhrman grade 1 and 2) with tumor size < 4 cm (pT1a) were retrieved from the archives over past 12 years (2000-2011). Slides from each case were re-reviewed by two independent pathologists to identify histomorphological features of CCPRCC. Representative tissue blocks are subjected for further immunohistochemistry studies using antibodies against cytokeratin 7 (CK7) and alpha-methylacyl-CoA racemase (AMACR).
Results: A total of 126 cases of stage T1a with low nuclear grade clear cell RCC were identified from 625 radical /partial nephrectomy specimens. Within 10 cases that show characteristic features of CCPRCC (such as tubular/papillary architecture and nuclei in linear arrangement away from basal aspect of cells), nine cases were confirmed by strong and diffusely immunoreactivity of CK7 and negative stain for AMACR. Among patients with CCPRCC, 7 are male and 2 are female. The mean age of patients at diagnosis was 52 years (range 35-81 years). Histologically, eight out of nine (89%) cases of CCPRCC contain different size cysts lined by single layer of cells that have moderate amount of clear cytoplasm or scant eosinophilic cytoplasm. Eight cases were previously diagnosed as “clear cell RCC” and one was diagnosed as “multilocular cystic RCC”.
Conclusions: In this retrospective study, 7% of previously diagnosed low grade and low stage clear cell RCC and multilocular RCC are found to be CCPRCC based on criteria for diagnosis of this newly recognized entity. The CCPRCC can be confused morphologically with other renal cell carcinomas, particularly clear cell carcinoma and its variants, when one is not aware of this new entity.
Category: Genitourinary (including renal tumors)

Tuesday, March 5, 2013 1:00 PM

Poster Session IV # 192, Tuesday Afternoon


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