The currently used diagnostic strategies, such as chest radiography, sputum cytology, and blood biomarkers (autoantibodies, complement fragments, circulating tumor DNA, carcinoembryonic antigen (CEA), cancer antigen 125 (CA-125), carbohydrate antigen 15.3 (CA15.3), cytokeratin-19 fragment (CYFRA 21-1), neuron-specific enolase (NSE), squamous cell carcinoma antigen (SCCA), and pro-gastrin-releasing peptide (ProGRP)) have insufficient sensitivity or specificity for an early and reliable diagnosis of LC [227]. This evidence concerns the gene CEACAM5 and neoplasm.