SMARCB1 and endometrioid adenocarcinoma: These tumors arise from endometrioid carcinomas, most commonly in a MMR-deficient (MMRd) background, by acquiring the following mutually exclusive alterations in the undifferentiated component: the co-mutation of ARID1B/ARID1A, SMARCA4 (BRG1) or SMARCB1 (INI1) [41].