However, there are prognostic differences within specific stages because of the biological heterogeneity of tumors; thus, additional tumor markers such as tumor grade, lymphovascular invasion, proliferation markers, estrogen and progesterone receptor (ER and PR) status, and human epidermal growth factor receptor 2 (HER2) overexpression have been suggested to provide a more precise prognosis of breast cancer[3–5]. Here, ERBB2 is linked to breast cancer.