Clinical tumor markers such as neuron-specific enolization enzyme (NSE), carcinoembryonic antigen (CEA), cytokeratin 19 (CYFRA21-1), and squamous cell carcinoma antigen (SCC) have demonstrated low sensitivity and specificity in the diagnosis of early-stage lung cancer, resulting in irreparable harm to the patient’s clinical diagnosis, treatment, and outcome. Here, CEACAM5 is linked to lung cancer.