[856] The Utility of PAX2 and Renal Cell Carcinoma Marker Immunohistochemistry in Distinguishing Papillary Renal Cell Carcinoma from Non-Renal Neoplasms with Papillary Features

DC Phan, SG Sharma, RM Cox, M Gokden, JK McKenney, N Gokden. University of Arkansas for Medical Sciences, Little Rock, AR; Stanford University, Stanford, CA

Background: PAX2 is a homeogene expressed during kidney development. It has been studied in primary and metastatic clear cell renal cell carcinoma (RCC). It has not been investigated in papillary (pap) neoplasms or in comparison to RCC marker (RCCma). We studied immunohistochemical (IHC) expression of PAX2 and RCCma in papillary RCC (P-RCC) and in a variety of non-renal papillary neoplasms (NRPN).
Design: 24 primary P-RCC (20 type I, 4 type II) and 66 NRPN {10 ovarian and 9 uterine serous pap (SP) carcinomas (Ca), 10 pap urothelial Ca, 10 cervical pap squamous cell Ca, 9 pap thyroid Ca, 5 pap squamous cell Ca of oral cavity, 2 pap intraductal mucinous pancreatic Ca, 3 choroid plexus papillomas, 2 myxopapillary ependymomas, 2 malignant meningiomas with pap features, 1 pituitary adenoma with pap features, 1 pap craniopharyngioma, 2 lung adenocarcinomas with pap features} were stained for PAX2 and RCCma. Nuclear staining for PAX2 and membranous staining for RCCma were scored semiquantitatively as: Negative: 0%, 1+: 1-25%, 2+: 26-50%, 3+: 51-100% of cells staining.
Results: 16/24 (66%) P-RCC were positive for PAX2, and 23/24 (95%) were positive for RCCma. The immunoprofiles of P-RCC were: PAX2+/RCCma+: 14/24 (58%), PAX2+/RCCma: 1/24 (4%), PAX2/RCCma+: 9/24 (38%), PAX2/RCCma: 0. Nine of 66 (13%) NRPN were positive for PAX2 {4/10 (40%) ovarian SPCa, 5/9 (68%) uterine SPCa}. RCCma was positive in 28/66 (42%), including 9/9 (100%) pap thyroid Ca, 8/10 (80%) ovarian SPCa, 4/9 (44%) uterine SPCa, 1/10 (10%) pap urothelial Ca, 1/2 (50%) pap intraductal mucinous pancreatic Ca, 3/3 (100%) choroid plexus papillomas, 1/1 (100%) pituitary adenoma with pap features, and 1/2 (50%) lung adenocarcinomas with pap features. The immunoprofiles of NRPN were: PAX2+/RCCma+: 7 of 66 (11%), PAX2+/RCCma: 2 of 66 (3%), PAX2/RCCma+: 21 of 66 (32%), PAX2/RCCma: 36 of 66 (54%). Positivity was variable between 1-3+.
Conclusions: PAX2 has lower sensitivity (66%), but higher specificity (86%) compared to RCCma (95 and 60%, respectively) for distinguishing P-RCC from NRPN. The sensitivity of PAX2+/RCCma+ immunophenotype was reduced to 58% with a slight increase in specificity (89%) for P-RCC. Therefore, PAX2 and RCCma IHC should be used and interpreted with caution in pap neoplasms, with particular attention to the possibility of ovarian and uterine SPCa, which can express both PAX2 and RCCma.
Category: Genitourinary (including renal tumors)

Tuesday, March 10, 2009 1:00 PM

Poster Session IV # 138, Tuesday Afternoon