PAX8 and mucinous adenocarcinoma: PAX-8, which was positive in 87% of primary ovarian carcinomas in one study and 0% of primary breast carcinomas, is the stain of choice, followed by WT-1, which was found to be positive in 85% of primary ovarian carcinomas and 2% of primary breast carcinomas, with the exception of mucinous carcinomas, which were found to be positive in 64% of cases [5, 11–13].