Surgeons should pay attention if a MTC patient has suspicious cervical sonographic results and CEA above 7.115 ng/mL and/or calcitonin above 13.185 pg/mL during early follow‐up, especially approximately 1 month after the surgery, which suggests potential occult metastases to the lateral compartment lymph nodes and a requirement for surgical removal, if required. Here, CEACAM5 is linked to medullary thyroid gland carcinoma.