[1018] Detailed Immunohistochemical (IHC) Characterization of the Recently Described Clear Cell-Papillary Renal Cell Carcinoma of the Kidney

DE Westfall, DJ Luthringer, R Alsabeh, RS Parakh, M Vankalakunti, MB Amin. Cedars-Sinai Medical Center, Los Angeles, CA

Background: Several renal epithelial tumors may have a combination of clear cell and papillary features including clear cell renal cell carcinoma (RCC), papillary RCC, translocation associated RCC and the recently described clear cell-papillary RCC (CP-RCC). The latter is a RCC with papillary and tubular architecture, exclusive clear cell cytology and low nuclear grade with nuclei arranged in a linear alignment away from the basal aspect of the cells. CP-RCC has a predilection for end stage renal disease (ESRD) although it rarely occurs in the sporadic setting. Only one series each of tumors in ESRD and sporadic settings has been described in the literature to date and these descriptions identify CP-RCC as a distinctive subtype of RCC with unique morphologic and cytogenetic features.
Design: A comprehensive analysis of contemporarily used IHC markers in the histologic subtyping of RCC was performed to identify the immunoprofile of CP-RCC. Eight cases of CP-RCC, four in ESRD and four in a sporadic setting were stained with a panel of CK7, AMACR, Pax2, CD10, RCC, high molecular weight cytokeratin (HMCK) and TFE3. The IHC profile was compared to eight cases of typical papillary RCC chosen specifically as they had areas of clear cell change.
Results: All cases of CP-RCC were positive for CK7 and negative for AMACR; all cases of papillary RCC were positive for AMACR and 50% of cases were positive for CK7. The immunoprofile of all other markers is outlined below.

CP-RCC ESRD3/30/30/33/44/40/3
Papillary RCC1/88/88/81/84/80/8

Conclusions: 1) The IHC expression profile of CP-RCC is identical in tumors occurring sporadically and in ESRD kidneys suggesting that these tumors, although occurring in different settings, are morphologically and immunohistochemically closely related. 2) The IHC profile of CP-RCC (CK7+, AMACR-, HMCK+) is distinct from that reported for RCC with overlapping histologic features - papillary RCC (CK7+, AMACR +, HMCK-), clear cell RCC (CK7-, AMACR-, HMCK-) and translocation associated RCC (CK7-, AMACR+, TFE3+). 3) The importance of this distinction is underscored by emerging different therapy/therapeutic targets for tumors with clear cell and papillary features - clear cell RCC (immunomodulation), translocation associated RCC (MET inhibitors) and papillary RCC (MET/VEGFR2 inhibitors and hepatocyte growth factor pathway inhibitor).
Category: Genitourinary (including renal tumors)

Tuesday, March 23, 2010 9:30 AM

Poster Session III # 156, Tuesday Morning


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