Although many gastric cancer biomarkers including carbohydrate antigen 72-4 (CA 72-4), alpha-fetoprotein (AFP), carbohydrate antigen 125 (CA 125), β-subunit of human chorionic gonadotropin (β-hCG), and pepsinogen I/II have been described, carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9) are still the most frequently used biomarkers in clinical practice for gastric cancer. The gene discussed is CEACAM5; the disease is gastric cancer.