[768] CAIX Expression in Renal Neoplasms: Correlation with Tumor Type and Grade

EM Genega, M Ghebremichael, R Najarian, Y Fu, Y Wang, C Grisanzio, S Signoretti. Beth Israel Deaconess Medical Center, Boston, MA; Harvard University & Dana Farber Cancer Center, Boston, MA; Brigham & Women's Hospital, Boston, MA

Background: Carbonic anhydrase IX (CAIX), a hypoxia-induced protein, is expressed in some renal cell carcinomas (RCC) and is reported to be an independent predictor of outcome. In this study, we assessed CAIX expression in renal neoplasms (RN) and correlated it with tumor type and grade.
Design: The study group consisted of primary and metastatic RN. The diagnosis and grade of the tumor were recorded from review of slides or pathology reports. Papillary RCC (PRCC) were classified as Type 1 or 2. CAIX immunostaining was performed on one representative section of tumor from each case with the M75 antibody. CAIX expression was divided into two categories, >85% tumor cells positive (high) or 85% tumor cells positive (low); cytoplasmic membrane staining was considered positive. Fisher's exact tests were used to determine associations between CAIX expression and tumor type and Fuhrman grade.
Results: Three hundred fifty-one cases were available for analysis; there were 302 primary RN, 42 metastatic RCC, and 7 cases site unknown. The distribution of tumor type was as follows: 186 clear cell RCC (CCRCC), 52 PRCC, 35 chromophobe RCC, 20 unclassified RCC (URCC), 26 oncocytomas, 2 metanephric adenomas, 1 urothelial carcinoma, 1 mixed epithelial and stromal tumor, and 1 angiomyolipoma. Twenty-seven cases were either unknown tumor type or more than 1 tumor type. Variable staining for CAIX was seen in CCRCC, PRCC and URCC. Only one chromophobe RCC showed focal, weak staining. No staining for CAIX was seen with other tumor types. High CAIX staining was seen in 71% of CCRCC compared to 7% of all other tumors. There was an association between CAIX positivity (high vs. low) and tumor type (CCRCC versus other) when all cases were considered (p<0.01), as well as primary (p<0.01) and metastatic (p=0.025) cases analyzed separately. In CCRCC, there was a correlation between CAIX and grade (p<0.01); more grade 1(92%), 2(85%) and 3(76%) tumors expressed CAIX than grade 4(42%) tumors. There was no statistically significant association between CAIX and grade of PRCC (p=0.282) or between CAIX and type of PRCC (p=1.00).
Conclusions: CAIX expression is more common in CCRCC than other tumor types and is associated with grade. CAIX may be a useful marker to distinguish CCRCC from chromophobe RCC. Although PRCC may express CAIX, there was no association with grade or type 1 or type 2 PRCC.
Category: Genitourinary (including renal tumors)

Tuesday, March 10, 2009 9:30 AM

Poster Session III # 76, Tuesday Morning