Following European Society for Medical Oncology (‘ESMO’) and National Comprehensive Cancer Network (‘NCCN’) guidelines, the treatment of choice for patients with metastatic GC is two-agent systemic chemotherapy, preferably a platinum/fluoropyrimidine doublet, in combination with targeted therapy or immunotherapy considering human epidermal growth factor receptor 2 (HER2) and programmed death-ligand 1 (PD-L1) status2,3. The gene discussed is ERBB2; the disease is gastric cancer.