PIK3CA and endometrial cancer: In PIK3CA-mutated endometrial cancers, preference for the type of activating gain-of-function mutation (R88Q, E452K, E454K, H1047R, M1043I; ref. 50) differed between the groups; PIK3CA R88Q was most frequent in Groups 2 and 3, and its nucleotide context is a POLE mutation signature (Supplementary Table S1).