Due to the high cost of full genetic analysis, the immunohistochemical (IHC) surrogate biomarkers, including estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor-2 (HER-2), and the Ki-67proliferation index, are routinely used to define these subtypes, which are major prognostic factors in guiding targeted therapy and predicting tumor response to neoadjuvant chemotherapy (NAC) (5, 6). The gene discussed is ERBB2; the disease is neoplasm.