According to numerous studies, protein biomarkers including carcino embryonic antigen (CEA), cytokeratin 19 fragment 21-1 (CYFRA21-1), and squa mous cell carcinoma antigen (SCC-Ag) can help diagnose ESCC, but they are insufficiently sensitive and specific to offer a meaningful diagnosis for ESCC [20,21]; therefore, new reliable biomarkers for ESCC are still needed. This evidence concerns the gene CEACAM5 and esophageal squamous cell carcinoma.