ERBB2 and cancer: Breast cancer (BC) mainly has four molecular subtypes which have been defined in the large part of the hormone receptor or other forms of protein involved or not involved in each type of cancer: 1) luminal A or HR+/HER2– (HR-positive/HER2-negative) 2) luminal B or HR+/HER2+ (HR-positive/HER2-positive) 3) HER2-positive 4) triple-negative or HR–/HER2– (HR/HER2-negative) (Eliyatkın et al., 2015).