Medullary thyroid carcinoma is mainly manifested as painless hard solid nodules in the thyroid gland when some patients are first diagnosed, and the main cause of medullary thyroid carcinoma is mutation of the RET proto-oncogene. When unilateral or bilateral thyroid masses, dyspnea, dysphagia, hoarseness, hand and foot twitching, carcinoid syndrome and other symptoms occur, medullary thyroid carcinoma should be alerted to occur. Women between the ages of 30 and 60 with a family history of parathyroid and adrenal gland tumors are vulnerable to medullary thyroid cancer. Symptoms of painless hard solid nodules: 1. unilateral or bilateral thyroid masses: SMTC is mostly manifested as single thyroid tumor; hereditary MTC is mostly manifested as bilateral multicenter thyroid tumor; 2. dyspnea and dysphagia: caused by large masses compressing the trachea and esophagus; 3. masses in the lateral neck area: are enlarged regional metastatic lymph nodes, and common metastatic sites include central neck group and lateral lymph nodes. The rate of lymph node metastasis is more than 75% in MTC patients whose lumps can be palpated by clinicians; 4. hoarseness: caused by tumor invasion of the laryngeal nerve; 5. hand and foot convulsions, caused by the decrease of blood calcium due to calcitonin; 6. facial flushing, palpitation, diarrhea, wasting and other carcinoid syndrome: easily seen in patients with extensive liver metastases, caused by various peptides and peptide hormones secreted by tumor cells; 7. liver, lung and bone metastases: tumor invades blood vessels and distant metastases occur. 7, lung and bone metastasis: tumor invades blood vessels and distant metastasis occurs, and up to 15% of patients have metastasis in distant septal sites, which is the main cause of death in MTC patients.