Thyroid cancer is divided into four major categories: papillary carcinoma, follicular carcinoma, medullary carcinoma, and undifferentiated carcinoma. The first two are collectively known as differentiated thyroid cancer (DTC), which accounts for more than 90% of thyroid cancers. Most DTCs are well differentiated, less aggressive, slow growing, and usually have a good prognosis with a 10-year survival rate of over 95%. And micro papillary thyroid cancer has a better prognosis. In a study of 18,445 PTMC patients followed for 19 years, the disease-related survival rate of patients with micro papillary thyroid cancer was 99.3% to 99.5%. Such a good prognosis is due to the fact that continuous medical advances have enabled many DTC patients to be detected at an early stage. Even patients with DTC who already have metastases are very fortunate. Because differentiated thyroid cancer originates from thyroid follicular cells, which still retain a certain function of iodine uptake, so that radioactive iodine becomes a natural target drug, which can be taken up by thyroid cancer cells in recurrent foci and metastatic foci in any part of the body after introduction, with concentrated firepower and little injury to other organs, which can play a therapeutic role and at the same time perform imaging to screen for new lesions and evaluate the efficacy. Therefore, “surgery + postoperative selective 131I therapy + thyroid stimulating hormone (TSH) suppressive therapy” has become the accepted treatment option for DTC. It has been demonstrated that 131I therapy given after surgical treatment of thyroid cancer can effectively remove residual thyroid tissue and cancer at the cellular level and prevent tumor recurrence. The literature reports that the recurrence rate of thyroid cancer is as high as 32.0% with surgery alone, 11% with surgery + oral thyroid hormone, and only 2.7% with surgery + 131I therapy + oral thyroid hormone. Foreign data reported that those who added 131I treatment after surgery had 3.8 ~ 5.2 times lower mortality rate and 4 times lower recurrence rate than patients with surgery alone. Among the other two types, medullary thyroid cancer does not have as good a prognosis as differentiated thyroid cancer, but the 5-year survival rate can reach 70% and the 10-year survival rate is about 50%. Only undifferentiated thyroid cancer has the worst prognosis and develops rapidly, with an average survival of 3-6 months. However, the proportion of undifferentiated cancer is very low at 1%-2%. Nowadays, although thyroid cancer is “highly prevalent”, the majority of thyroid cancer has a good prognosis, so we really don’t need to be afraid of it.