ERBB2 and breast cancer: Human epidermal growth factor receptor 2 (HER2), a widely known biomarker for breast cancer prognosis assessment, has become one of the most important tools for oncologists to decide a patient’s treatment, as monoclonal antibody-based therapies designed to block HER2 activity, such as trastuzumab or pertuzumab, and tyrosine kinase inhibitors (TKIs), like lapatinib, have shown to dramatically reduce disease burden and improve efficacy outcomes in different breast cancer settings [1,2,3,4,5].