MTC can synthesize and secrete a variety of bioactive substances, such as Ctn and Carcinoembryonic Antigen (CEA), that, in addition to the neck US and intraoperative inspection, can be used like predictors of tumor extent in lymph nodes and eventually of the risk of recurrence [9,10,11,12]. Here, CEACAM5 is linked to medullary thyroid gland carcinoma.