Commonly used biomarkers of lung cancer tested individually or in panels of several combined biomarkers include the well-known cytokeratin fragment 19 (CYFRA 21-1), carcinoembryonic antigen (CEA), squamous cell carcinoma antigen (SCCA), and carbohydrate antigen 125 (CA125) [72,73]. Here, CEACAM5 is linked to lung cancer.