Additionally, blood tumor markers such as Carcinoembryonic Antigen (CEA), Squamous Cell Carcinoma Antigen (SCC), Cytokeratin-19 Fragment Antigen 21 − 1 (CYFRA 21 − 1), and Gastrin-releasing Peptide Precursor (ProGRP) [18], as well as novel liquid biopsy markers like single-cell sequencing [19], seven-antibody detection for lung cancer [20], DNA methylation levels [21], and circulating tumor cells [22], are integrated into clinical diagnostic protocols. This evidence concerns the gene CEACAM5 and lung cancer.