PIK3CA and Epidermal Inclusion Cyst: Compared to control mice (Figs 2C and S2A), histological analysis of LtfCre0/+; (Gt)R26Pik3ca*H1047R; Trp53fl/fl mice (henceforth referred to as TP53/PIK3CA mutant mice) revealed features of hyperplasia, adenocarcinoma, and endometrial intraepithelial carcinoma (EIC) within luminal and glandular areas (Figs 2D and S2B).