PIK3CA and gastric cancer: Recent whole‐exome and whole‐genome sequencing of gastric cancer and diffuse‐type gastric cancer revealed significant mutation of TP53, PTEN, CTNNB1, ARID1A, PIK3CA, FAT4, MUC6, CTNNA2, and other genes are in gastric cancer 10, 11, 12, 13, 14, 15.