ARID1A and endometrioid adenocarcinoma: Endometrial Cancer: The rate of ARID1A mutation in low-grade endometrioid adenocarcinomas is 47%, while in high-grade endometrioid adenocarcinomas, serous adenocarcinomas, and carcinosarcomas, it is 60%, 11%, and 24%, respectively [16,82,83,84].