ESR1 and endometrioid adenocarcinoma: In conclusion, this study with a large sample size has found that the majority of serous carcinomas in both malignant and borderline epithelial ovarian cancers, as well as endometrioid carcinoma in malignant epithelial ovarian cancer, were ER and PR positive in this Chinese population, and the proportion of ER or PR positive tumours were similar to that previously reported in other ethnicities.