CEACAM5 and medullary thyroid gland carcinoma: The article summarizes the positive rates of various immune markers in MTC: TTF-1 (99.0%+), CT (85.4%+), Syn (98.7%+), CgA (81.9%+), CEA (88.8%+), and the Ki-67 positive rate was ≤10% in 95.1% of the patients.