CEACAM5 and small cell lung carcinoma: Previous studies have reported various biomarkers of SCLC patients as candidates of prognostic factors, such as neuron-specific enolase (NSE), chromogranin A (cGA), neural cell adhesion molecule (NCAM), caspase cleaved cytokeratin 19 (CYFRA21.1), tissue polypeptide antigen (TPA), carcinoembryonic antigen (CEA), lactate dehydrogenase (LDH), and neutrophil-to-lymphocyte ratio (NLR) [13, 14].