PIK3R1 and serous adenocarcinoma: Mutations more commonly identified in endometrioid adenocarcinomas include ARID1A and POLE, while those more commonly identified in serous adenocarcinomas include TP53, FBXW7 and PPP2R1A. Alterations in PIK3CA are frequently found in both endometrioid and serous histologies, whereas PTEN, PIK3R1, CTNNB1 and KRAS are often mutated in endometrioid but rarely in serous histologies36–38.