ERBB2 and breast carcinoma: Breast cancer could be classified into four primary molecular subtypes, defined by the presence or absence of hormone receptors (HR) and other types of proteins: (1) luminal A or HR+/HER2-; (2) luminal B or HR+/HER2+; (3) triple-negative or HR-/HER2-; and (4) HER2-positive [26].