PIK3R1 and neoplasm: Of the key genes involved in ten canonical tumor-related pathways and DDR pathways, PTEN, ARID1A, and PIK3CA had the highest mutation frequency in both dMMR (90.5%, 74.3%, 68.9%) and pMMR (67.4%, 34.9%, 62.8%) ECs, followed by KRAS (28.4%), PIK3R1 (25.7%), FAT1 (23.0%), ATM (21.6%), TP53 (20.3%), CREBBP (17.6%), and FBXW7 (17.6%) in dMMR cohort, and TP53 (34.9%), PIK3R1 (27.9%), ATM (25.6%), CTNNB1 (23.3%), NF1 (23.3%), POLE (23.3%), and FBXW7 (20.9%) in pMMR cohort.