CEACAM5 and medullary thyroid gland carcinoma: The carcinoembryonic antigen (CEA) was additionally determined in 14 of the MTC patients at the time of the first screening: values above the reference range (up to 3.8 ng/mL) were found in 9/14 (64%) with a range from 4.1 to 42.2 ng/mL (Supplementary Table S1).