ERBB2 and breast carcinoma: According to the molecular classification of breast cancer, which categorizes tumors on the basis of the presence of hormonal receptors (estrogen and progesterone) and human epidermal growth factor receptor 2 (HER2) expression, the luminal A subtype is predominant in the United States, affecting 66% of patients, followed by the luminal B (10%), basal or triple-negative (10%), and HER2-positive (4%) subtypes [4].