The current markers widely used in the clinical screening or diagnosis of lung squamous cell carcinoma, adenocarcinoma, and small cell carcinoma include carcinoembryonic antigen (CEA), squamous cell carcinoma antigen (SCC), neuron-specific enolase (NSE), carbohydrate antigen 125 (CA125), cytokeratin-19 fragment (CYFRA21-1), and prosecretin-releasing peptide (proGRP) [12]. The gene discussed is CEACAM5; the disease is squamous cell lung carcinoma.