PIK3R1 and adenoma: In total 93 polypoid adenomas and 106 flat adenomas were analyzed for 13 genes (BRAF, NRAS, KRAS, PIK3CA, PIK3R1, EGFR, PTEN, MAP2K4, SMAD4, FBXW7, CTNNB1, STK11 and PDGFRA) at 82 nucleotide positions.