Value of PAX-8 and SF-1 Immunohistochemistry in the Distinction Between Female Adnexal Tumor of Probable Wolffian Origin and its Mimics.

Female adnexal tumors of probable wolffian origin (FATWOs) are rare. They can closely mimic endometrioid adenocarcinomas with a prominent spindle cell component and Sertoli cell tumors (SCTs). To further define their immunohistochemical profile and origin, we investigated the expression of PAX-8, PAX-2, and GATA binding protein 3 (GATA-3) (wolffian markers) and of steroidogenic factor-1 (SF-1) (sex-cord stromal marker) in FATWOs. We also studied the expression of PAX-8 and PAX-2 in endometrioid adenocarcinomas; of SF-1 in Sertoli-Leydig cell and SCTs; and of PAX-8, PAX-2, GATA-3, and SF-1 in rete ovarii-a proposed site of origin for FATWOs. A database search yielded 8 FATWOs, 18 ovarian/tubal/paraovarian endometrioid adenocarcinomas, and 8 ovarian Sertoli-Leydig cell and SCTs. Eleven cases with rete ovarii sections were included. Of the FATWOs studied, all were negative for PAX-8, PAX-2, GATA-3, and SF-1. Of the endometrioid adenocarcinomas studied, PAX-8 was positive in all and PAX-2 was positive in 57%. Of the Sertoli-Leydig cell and SCTs, all were positive for SF-1 except one. The rete ovarii were positive for PAX-8, weakly positive for SF-1, and negative for PAX-2 and GATA-3. Our study suggests that PAX-8 and SF-1 can be helpful in the distinction between FATWOs and endometrioid adenocarcinomas and SCTs, respectively. Our results do not support a Mullerian or sex-cord stromal or rete ovarii origin for FATWOs. It is curious, however, that FATWOs do not express wolffian markers-it is possibly related to their origin from a distinctive portion of the wolffian duct.