We performed a research on Pubmed/Medline, Cochrane Library, and Scopus using the keywords “gastric cancer” OR “gastric adenocarcinoma” OR “gastroesophageal cancer” AND “HER2” OR “human epidermal growth factor receptor” OR “trastuzumab” OR “trastuzumab deruxtecan” OR “margetuximab” OR “ZW25” OR “trastuzumab emtansine”. Here, ERBB2 is linked to gastric cancer.