CEACAM5 and neoplasm: Presently, conventional antigenic tumor markers, such as carcinoembryonic antigen (CEA) and carbohydrate antigen (CA) 19-9, show low sensitivity or specificity in varying degrees in the screening and diagnosis of ESCC (8, 9) and the “Guideline for the diagnosis and treatment of esophageal cancer (2022)” (6) clearly stated that clinical ESCC-specific serum tumor markers remained to be established.