PIK3CA and cancer: In result, we observed similar mutational frequencies in some canonical cancer driver genes between OCCC and ECCC cohorts, such as PIK3CA (OCCC 53% vs. ECCC 40%), TP53 (OCCC 38% vs. ECCC 43%), KRAS (OCCC 21% vs. ECCC 13%), APC (OCCC 9% vs. ECCC 13%), and KMT2C (OCCC 18% vs. ECCC 13%), while only the mutation rate of ARID1A in OCCC was significantly higher than that in ECCC (p < 0.01; Fig. 1B).