[1156] PAX-8 Expression in Gynecologic and Breast Carcinomas.

Jing Yu, Anna H Woodard, Anca V Florea, David J Dabbs, Esther Elishaev, Sushil Beriwal, Rohit Bhargava. University of Pittsburgh Medical Center, PA

Background: The differential diagnosis among breast carcinomas and gynecologic carcinomas, including ovarian, endometrial and endocervical carcinomas, can be challenging when distinct morphologic features are not present, because they often share the phenotypic profiles of the common immunohistochemical markers (e.g. CK7+/ER+/CK20 negative). PAX8, a transcription factor, has been recently shown to be expressed in ovarian carcinomas, but not breast carcinomas. The aim of this study is to examine the expression profile of PAX8 in a spectrum of gynecologic carcinomas and a variety of breast carcinomas.
Design: A total of 145 gynecologic carcinomas (including 55 endometrial carcinomas, 37 endocervical carcinomas, and 53 ovarian carcinomas) and 184 breast carcinomas (including 170 invasive ductal carcinomas, 12 invasive lobular carcinomas, and 2 mixed ductal and lobular carcinomas) were retrieved for the study. Tissue microarrays of the tumors were stained with PAX8 rabbit polyclonal antibody. All tumors were semi-quantitatively scored using H-score method where the score combining intensity and percentage of positive cells ranges from 0 (negative) to 300 (diffuse strong reactivity).
Results: All 184 breast carcinoma were negative for PAX8. Among the 145 gynecologic carcinomas, PAX8 expression (H-score > 10) was found in 33 of 39 endometrial endometrioid carcinomas, 14 of 16 endometrial non-endometrioid carcinomas (including 8/8 serous carcinomas, 3/3 clear cell carcinomas, 2/3 undifferentiated carcinomas, 1/1 mixed serous and clear cell carcinoma, and 0/1 MMMT), 20 of 37 endocervical carcinomas (including 0/4 adenoid basal, 9/15 endocervical, 6/9 endometrioid, 0/2 mesonephric, 2/3 serous, and 3/4 villoglandular variants), 12 of 14 ovarian serous carcinomas, 24 of 35 ovarian clear cell carcinomas, and 2 of 4 ovarian endometrioid carcinomas.

PAX 8 Expression in Gynecologic Tumors
Site and tumor type% of (+) casesAverage H-score of (+) cases
Endometrial endometrioid8592
Endometrial non-endometrioid8896
Endocervical carcinoma5666
Ovarian clear cell6991
Ovarian endometrioid5090
Ovarian serous8686

Conclusions: PAX8 nuclear expression (even weak) in a CK7+/ER+/CK20 negative tumor supported a gynecologic primary tumor rather than a breast carcinoma. Among gynecologic tract tumors, PAX8 was more often positive in endometrial and ovarian tumors compared to cervical tumors (p=0.011). PAX8 expression was generally higher in endometrial tumors compared to cervical tumors (p=0.004). Unlike WT1 (specific for ovarian serous morphology), PAX8 expression was not specific to any morphology.
Category: Gynecologic & Obstetrics

Tuesday, March 1, 2011 1:00 PM

Poster Session IV # 121, Tuesday Afternoon


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