CEACAM5 and esophageal squamous cell carcinoma: However, there are only a few molecules that have been clinically validated as diagnostic biomarker for ESCC.5 Conventional tumor markers, such as carcinoembryonic antigen (CEA), E-cadherin, CA-125, and alpha-fetoprotein, have been successfully employed as a convenient diagnostic assays to detect certain cancers.6 Nonetheless, these tumor markers cannot provide sufficient sensitivity and specificity in early-stage ESCC detection.7,8 Thus, there is an urgent need to identify the novel accurate biomarkers with less invasiveness for the early-stage ESCC diagnosis.