Medullary thyroid carcinoma is a malignant tumor originating from the follicular paraganglioma cells of the thyroid gland, which is a relatively rare type of thyroid tumor, accounting for about 3% to 8% of thyroid tumors. These diseases are more common in 30-40 years old. It is more common in women than men, and the ratio of male to female incidence is about 1:1.5. Classification: Medullary thyroid carcinoma can be divided into two categories: sporadic and hereditary, with sporadic accounting for about 70% to 80% of medullary thyroid carcinoma and hereditary accounting for about 20% to 30%. Hereditary medullary thyroid carcinoma is an autosomal dominant disease. It is recommended that all patients with medullary thyroid carcinoma and their first-degree relatives be tested for the proto-oncogene RET mutation gene. Clinical manifestations: It is difficult to distinguish preoperatively from other types of thyroid diseases. Most patients are seen for neck masses (thyroid nodules), which can invade the laryngeal nerves and trachea and cause hoarseness and breathing difficulties. Lymph node metastasis can occur at an early stage, so enlarged lymph nodes in the neck are also a common first symptom. Medullary thyroid cancer tumor cells can secrete 5-hydroxytryptamine, histamine, prostaglandin and adrenocorticotropic hormone-like substances, which lead to endocrine symptoms such as painless and persistent diarrhea, bone pain and facial flushing in some patients. A neck mass with diarrhea is a more specific clinical manifestation of medullary thyroid carcinoma. Among them, Marfan’s physiognomy (elongated limbs, eye disease, cyanotic lips and other manifestations) and mucosal ganglioneuropathy are important features of medullary thyroid carcinoma. Some patients with hereditary medullary thyroid carcinoma have pheochromocytoma manifestations such as malignant hypertension as the first symptom. Examination methods: Ultrasound examination of thyroid alone is difficult to distinguish from other thyroid cancers. If the cancer is large, ultrasound-guided puncture examination is a highly sensitive means to confirm the diagnosis. Preoperative calcitonin greater than 100ng/L can be diagnosed as medullary thyroid cancer. Patients need to undergo intraoperative cryopathological examination to further confirm the diagnosis. If lung, liver or bone metastasis is suspected, CT of lung or whole body bone scan should be performed to determine. Treatment: Since medullary thyroid cancer is not sensitive to radiotherapy and parafollicular thyroid cells do not absorb iodine, 131I radiation therapy is not effective for medullary thyroid cancer, so surgery is still the preferred radical treatment for medullary thyroid cancer. Foreign scholars agree that medullary thyroid carcinoma has the possibility of intra-glandular dissemination and the recurrence rate is low after total thyroidectomy. Therefore, the best surgical procedure is total thyroidectomy + lymphatic dissection in the central region for both disseminated and hereditary medullary thyroid carcinoma. If the medullary thyroid cancer is hereditary, even if the initial lesion is unilateral, the opposite lobe can develop within a short time after surgery, and total thyroidectomy is recommended. Survival rate: The cumulative survival rates of medullary thyroid cancer were 87.4%, 74.6% and 54.2% at 5, 10 and 15 years, respectively, calculated by the life table method. Univariate analysis revealed that gender, age, bilateral involvement of primary foci, primary foci >4 cm in diameter, extraperitoneal invasion of the thyroid, distant metastases, and the degree of surgical thoroughness had an impact on prognosis. The prognosis was worse for bilateral involvement of primary foci than unilateral, worse for those with primary foci >4 cm in diameter, significantly worse for those with distant metastases, and significantly worse for surgical completeness. In contrast, the differences in prognosis were not statistically significant for different first symptoms, staging of each type, different surgical approaches for primary foci, surgical approach to cervical lymphatic clearance, whether the cervical lymph nodes metastasized (confirmed by postoperative pathology), treatment (surgical operation + chemotherapy), presence of recurrence, and presence of endocrine symptoms such as diarrhea.