PIK3CA and cancer: The histological and molecular phenotypes are similar in the expression of TP53, ER, PR, HIF1 β and napsinA between OCCC and ECCC (Ju et al., 2018; Lim et al., 2015), while mutation frequencies of ARID1A in our OCCC cohort were observed significantly higher than in ECCC cohort, and mutational frequencies in some canonical cancer driver genes are similar between these two cohorts, such as PIK3CA, TP53, KRAS, APC, and KMT2C, indicating that they might play pivotal roles in clear cell carcinoma tumorigenesis.