The prognosis of patients with stage IV breast cancer can be different depending on the molecular subtype of the disease (hormone receptor (HR) and human epidermal growth factor receptor 2 (HER2) status), site(s) of metastasis, the number of sites involved in metastasis, the status of the lymph nodes, the previous treatment received, and the pathological and clinical characteristics of the disease (10, 11). This evidence concerns the gene ERBB2 and breast carcinoma.