AFP has been used as a biomarker in clinical screening, diagnosis, prediction, and treatment evaluation of hepatocellular carcinoma (HCC).11 At around the same time (in 1965), Goldenberg and Freeman found that carcinoembryonic antigen (CEA) in fetal colon mucosa12 contributed a crucial part in tumor diagnosis and prognosis evaluation of lung cancer,13 breast cancer,14 ovarian cancer,15 colorectal cancer (CRC),16 etc. The discovery of AFP and CEA has promoted the clinical application of tumor biomarkers. The gene discussed is CEACAM5; the disease is lung cancer.