Biomarkers, including mucin 1, claudin 18.2 (CLDN 18.2), human epidermal growth factor receptor 2 (HER2), NK receptor group 2, epithelial cell adhesion molecule, mesothelin (MSLN), and carcinoembryonic antigen, play pivotal roles in the diagnosis and progression of GC. The gene discussed is MSLN; the disease is gastric cancer.