ERBB2 and breast cancer: Through these analyses, breast cancers have been stratified into four subtypes: luminal A, luminal B, human epidermal growth factor receptor-2 positive (HER2 + ), and basal-like.2, 3Despite the translational application of the molecular stratification of breast cancer, many patients develop resistance to treatments and recurrence, which instigates research that seeks new biomarkers of prognosis and response to chemotherapy.4