ARID1A and endometrioid adenocarcinoma: IHC staining of 6 EC cases (5 endometrioid carcinoma and 1 carcinosarcoma) with DICER1 hotspot mutations [10] only identified ARID1A loss in one endometrioid carcinoma case, but neither SMARCA4 nor ARID1B was lost in any of the 6 cases.