CEACAM5 and esophageal squamous cell carcinoma: Currently, cytokeratin 19 fragment (CYFRA 21–1), squamous cell carcinoma antigen (SCC‐Ag), carcinoembryonic antigen (CEA), and carbohydrate antigen 19–9 (CA19‐9) have been utilized as common serum tumor markers of ESCC, but these routine biomarkers have multiple shortcomings such as low detection sensitivity and susceptibility to environmental factors.5, 6