ERBB2 and gastric cancer: In breast and gastric cancers, Erb-b2 receptor tyrosine kinase 2 (ERBB2) known as Human epidermal growth factor receptor 2 (HER2) protein overexpression and/or gene amplification is detected in some cases, and significant prognostic improvement has been achieved using therapeutic drugs targeting HER2 (eg, trastuzumab) [6].