PIK3CA and gastric cancer: In the present study, we analyzed a large cohort of clinically well-characterized gastric cancers for the presence of mutations in the exons 9 and 20 of PIK3CA gene by direct sequencing and PIK3CA amplification by real-time quantitative PCR, and correlated the presence of PIK3CA mutations and amplification with clinicopathological characteristics and clinical outcome of gastric cancer patients.