Postoperative follow-up should be monitored separately for 2 kinds of cancers: the follow-up for MTC mainly monitors serum calcitonin and CEA, and if it drops to normal after operation, the prognosis will be better; if it continues to rise, it is necessary to check the residual or metastatic focus. The gene discussed is CEACAM5; the disease is medullary thyroid gland carcinoma.