ESR1 and endometrioid adenocarcinoma: Similarly, in clear cell adenocarcinoma, a particular histological type of endometrial cancer, the levels of estrogen receptor (ER), progesterone receptor (PR) and Ki-67 are similar to those in serous adenocarcinoma while p53 is significantly lower, whereas ER and PR are significantly lower, Ki-67 is significantly higher and p53 tends to be higher compared to endometrioid adenocarcinoma (12).