CEACAM5 and lung adenocarcinoma: Currently used for clinical screening of lung adenocarcinoma tumor markers with carcinoembryonic antigen (CEA), cytokeratin-19 fragment (CYFRA21-1) and neuron-specific enolase (NSE) and so on, but these protein markers are prone to false positive, and their specificity and sensitivity are not high (Yuan et al., 2022).