Commonly used immunological markers are similar to those used in other types of small cell carcinoma, including neuronal specific enolase (NSE), chromogranin A (CgA), synaptophysin (Syn), cytokeratin, nerve cell adhesion molecule (CD56), and epithelial cell markers, including carcinoembryonic antigen. This evidence concerns the gene CEACAM5 and small cell carcinoma.