PIK3CA and esophageal squamous cell carcinoma: Consistent with the previous studies, this study also confirmed the frequent mutation of TP53, ZNF750, FAT1, PTCH1, EP300, FAT2, FBXW7, KMT2D, NFE2L2, NOTCH1, PIK3CA, RB1, RIPK4 and TP63 in ESCC patients (Chang et al., 2017; Sawada et al., 2016; Qin et al., 2016).