ERBB2 and breast cancer: In addition to the application of conventional therapy, the non-specific chemotherapy of breast cancer is supplemented with targeted drugs according to the molecular subtypes of the disease, namely: (i) the use of estrogen antagonists, like tamoxifen, fulvestran or aromatase inhibitors in estrogen positive tumors and (ii) the administration of anti-HER2 antibodies, like trastuzumab and tyrosine kinase inhibitors (TKI), like lapatinib in HER2 positive tumors.