Human carcinoembryonic antigen (CEA) belongs to a family of membrane glycoproteins that are overexpressed in many carcinomas. It functions in vitro as a homotypic intercellular adhesion molecule and can inhibit differentiation when expressed ectopically in myoblasts. It was originally described as a glycoprotein molecule with an oncofetal expression pattern. It is a member of a family of closely related molecules, whose genes reveal a high degree of sequence similarity. The CEA family shows structural resemblance to, and can be placed within, the immunoglobulin superfamily. CEA may function as a cell adhesion molecule, which could play an important role during embryogenesis and possibly also during tumor development. Despite its presence in some normal tissues, its concentration in serum is a clinically useful parameter, especially in the postoperative monitoring of colonic tumor patients. It maps to 19q13.1-q13.2 region of human chromosome. It is found in adenocarcinomas of endodermally derived digestive system epithelium and fetal colon.