The addition of anti-HER2 (Human Epidermal Growth factor 2) molecules such as trastuzumab in patients with overexpression and/or gene amplification of HER2 in tumors, has deeply modified the evolution of the metastatic disease, leading to an increase in OS (Overall Survival) to 37.6 month [4]. The gene discussed is ERBB2; the disease is metastatic neoplasm.