ESR1 and endometrioid adenocarcinoma: In a study of 40 grade 3 endometrioid carcinomas and 24 serous carcinomas 17, estrogen receptor (ER), progesterone receptor (PR), p16, monoclonal carcinoembryonic antigen, and vimentin were expressed in 50% versus 54%, 42% versus 54%, 25% versus 92%, 3% versus 13%, and 81% versus 83% of tumors, respectively.