It was reported that the positive expression rate of CEA in MTC was also very high, and its concentration was closely related to the progression and prognosis of MTC, which has increasingly become an important indicator in the diagnosis and treatment of MTC.5, 8, 9 A recent Canadian study of Canadian also reported that preoperative CEA level was closely related to tumor size, TNM stage, regional lymph node metastasis, biochemical cure, and survival rate.9 The results of our study demonstrate that serum CEA in MTC patients with LLNM was significantly higher than that in the group without LLNM. Here, CEACAM5 is linked to neoplasm.