Based upon immunohistochemical staining for key proteins’ expression, breast tumors are considered to contain at least 1% of the following genes: human epidermal growth factor receptor 2 (HER2, Erbb2 gene), estrogen receptor (ER), and progesterone receptor (PR, Pgr gene) (Hammond et al., 2010). The gene discussed is ERBB2; the disease is breast neoplasm.