We used the serological results from the first postoperative follow‐up in the calculation, with a median time of 35 days after the surgery, and found that a cut‐off value of 7.115 ng/mL for postoperative CEA and 13.185 pg/mL for postoperative calcitonin are useful to distinguish the presence of LLNM in MTC patients. This evidence concerns the gene CEACAM5 and medullary thyroid gland carcinoma.