ERBB2 and gastric cancer: Trastuzumab is a humanized monoclonal antibody that targets HER2 to inhibit HER2-mediated signaling transduction, and is widely used in metastatic breast cancer and advanced GC patients with high HER2 expression levels to achieve survival advantage3,11,12; however, the fact that only 7%–34% GC tissue exhibits high HER2 expression limited trastuzumab use in GC patients3,8,13.