Although increasing incidences of central nervous system (CNS) metastases have been reported in Her2-overexpressing BC due to the high anticancer effect of systemic trastuzumab (Her2 monoclonal antibody) without penetration of the blood-brain barrier, it is uncertain whether Her2 positivity in GC increases the risk of CNS metastases (7). The gene discussed is ERBB2; the disease is breast cancer.