ERBB2 and breast cancer: Human epidermal growth factor receptor 2 (HER-2), a member of the EGFR family, is a tyrosine kinase that localizes to cell membrane and conducts extracellular-intracellular signaling to regulate cell growth and differentiation, as well as the development of cancer.26,27 At present, HER-2 expression has been detected in various tumors, such as esophageal and gastric cancer, breast cancer, and ovarian cancer.28–30 Therefore, HER-2 is a crucial target for molecular-based treatment of EC.