ERBB2 and breast cancer: The expression of specific immunohistochemical biomarkers, such as hormone receptors (HR) and human epidermal growth receptor 2 (HER2), allows the diagnosis of BC into specific molecular subtypes: Luminal A, Luminal B, HER2-enriched and Triple Negative Breast Cancer (TNBC) type, with distinct phenotype, treatment strategies and clinical results [3,5,6].