When breast cancer treated with anti-HER2 target therapies, such as trastuzumab, pertuzumab, and tyrosine kinase inhibitor lapatinib and neratinib, they have been shown to significantly improve survival, but without appropriate anti-HER2 therapy, HER2-amplified tumors are associated with poor prognosis [16,17,18,19,20,21,22]. The gene discussed is ERBB2; the disease is breast cancer.