These cells secrete calcitonin (CTN) and carcinoembryonic antigen (CEA), which are used as biomarkers for the diagnosis and follow-up of MTC, along with other mediators (such as adrenocorticotropic hormone, ACTH) that cause paraneoplastic syndromes [1,2]. This evidence concerns the gene CEACAM5 and medullary thyroid gland carcinoma.