The long-term outcomes of metastatic breast cancer may be influenced by various biological features such as the age at initial diagnosis; status of hormone receptors (HRs), including estrogen receptor (ER), and/or progesterone receptor (PR), as well as human epidermal growth factor receptor 2 (HER-2); and the numbers and sites of metastases [2, 3]. This evidence concerns the gene ERBB2 and breast cancer.