The search terms included “HER2 positive” OR “HER2 expressing” AND “gastric cancer” OR “gastroesophageal junction adenocarcinoma” OR “gastroesophageal junction cancer”; the search was restricted to English-language articles published between September 1, 2014, and December 31, 2024. The gene discussed is ERBB2; the disease is gastroesophageal junction adenocarcinoma.