CEACAM5 and lung carcinoma: Serum tumor markers such as cytokeratin 19 fragment (Cyfra21-1) and carcinoembryonic antigen (CEA) are commonly used to screen for lung cancer, disease monitoring and prognosis, which are recommended by both the National Academy of Clinical Biochemistry (NACB) and European Group on Tumor Markers (EGTM) [14].