According to the 2011 St Gallen International Expert Consensus on the Primary Therapy of Early Breast Cancer, breast cancer can be classified into four subtypes based on immunohistochemical evaluation of hormone receptors (HRs), including the estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) (1). The gene discussed is ERBB2; the disease is breast carcinoma.