Gastric cancer (GC) is the fifth most prevalent cancer globally, and the second most common cancer in China.1 Approximately 15–30% of advanced gastric or gastroesophageal junction adenocarcinomas exhibit amplification or overexpression of the human epidermal growth factor receptor 2 (ERBB2/HER2).2 The heterogeneity of this biomarker poses substantial challenges for effective treatment, with responses varying widely among patients. This evidence concerns the gene ERBB2 and gastroesophageal junction adenocarcinoma.