PIK3CA and digestive system neoplasm: The gene panel used was designed for genomic analysis of gastrointestinal tumours and comprised amplicons of relevant DNA regions from 12 genes including BRAF, DDR2, ERBB2, HRAS, KEAP1,KRAS, NFE2L2,NRAS,PIK3CA, PTEN, RHOA and TP53 (see Supplemental Table S2).