CEACAM5 and medullary thyroid gland carcinoma: Spearman analysis showed that the levels of serum Ctn, CEA, and NSE in patients with MTC were positively correlated with each other (rCtn‐CEA = 0.871, rCtn‐NSE = 0.407, rCEA‐NSE = 0.465, all P < .001).