ERBB2 and breast cancer: ERBB2 overexpression / amplification are reported in multiple malignancies such as breast cancer, gastric cancer, esophageal cancer, endometrial cancer and so on, and its high expression often implies unfavorable prognosis of the patients; importantly, targeting ERBB2 has been applied in clinical practice to treat some cancers such as breast cancer and gastric cancer (Moasser, 2007; Wang, 2017).