[806] p63 Is Useful in Distinguishing Collecting Duct Renal Carcinoma from Its Morphologic Mimics

JC Carvalho, DG Thomas, JB McHugh, RB Shah, LP Kunju. University of Michigan, Ann Arbor, MI

Background: Renal cell carcinoma (RCC), collecting duct type (CDC) is a rare aggressive subtype of RCC, arising in the medulla of the kidney. CDC shares overlapping morphology with neoplasms that can involve renal hilum including invasive urothelial carcinoma (UC), Type 2 papillary renal cell carcinoma (PRCC) and high-grade clear cell renal cell carcinoma (CRCC). Accurate classification, specifically distinction of these RCC variants from UC is critical, as therapeutic approaches differ.
Design: A tissue microarray with 8 CDCs, 18 invasive UCs, 18 PRCCs and 20 CRCCs was immunostained with CK7, CD10, RCC, AMACR, PAX2, CAIX, p63, vimentin and S100A1. Expression was characterized as 0 (<10%), 1(focal, 10-50%), or 2 (diffuse, >50%) and data was evaluated using a cluster algorithm mathematical approach.
Results: Cluster analysis sorts the tumors into four groups. A majority (63%) of CDC form a distinct group with diffuse strong CK7 expression, variable PAX2 and lack of reactivity with other markers. Almost all (94%) UC cluster together with strong diffuse reactivity for p63 and CK7 and absent to minimal staining with renal markers (CD10, RCC, PAX2, AMACR, and CAIX) and vimentin. The remaining two groups are predominantly a mixture of PRCC and CRCC that differ based on expression of renal markers. Both these clusters lack p63, have minimal to absent CK 7 expression and strongly express vimentin. The remaining CDC cases (27%) segregate with the two clusters of PRCC and CRCC due to lack of CK7 expression. Overall, 63% of CDC expressed PAX2. Staining results are summarized in the table. S100A1 had minimal utility and was excluded from analysis.

Antibody Percentages of Four Tumor Types
Collecting Duct RCCUrothelial CarcinomaType 2 Papillary RCCClear Cell RCC
CA IX13245095

Conclusions: p63 is most useful in the distinction of morphologic mimics of CDC. Invasive UC and CDC have overlapping immunohistochemical profiles but can be differentiated by intense p63 expression in UC. PAX2 is rarely positive (6%) in UC; is variably expressed in CDC, PRCC and CRCC and may be helpful in separating UC from all other RCCs when positive. No unique immunohistochemical marker or panel of markers can differentiate PRCC from CRCC.
Category: Genitourinary (including renal tumors)

Tuesday, March 23, 2010 9:30 AM

Poster Session III # 146, Tuesday Morning


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