PIK3CA and esophageal squamous cell carcinoma: In the 7 cohorts of ESCC patients included in this analysis, 47 mutated genes were considered driver genes, but only 7 genes (TP53, NOTCH1, CDKN2A, ZNF50, NFE2L2, PIK3CA and RB1) were considered driver genes in the majority of studies; some genes, such as FAT1, FAT2, PTEN, EP300, FBXW7, APS31, MUC16 and RP&15, were considered driver genes only in a minority of studies [31].