Cool nodules are nodular tissues that do not absorb iodine, so there is no radioactivity at the nodule. About 20% of such nodules are cancerous. For those that are solitary and not very clearly demarcated from the surrounding tissues, cancer is more likely. Combined with the measurement of serum calcitonin, the diagnosis rate can be improved. Cool nodules are mostly seen in undifferentiated thyroid carcinoma, medullary carcinoma, cystic changes of the thyroid gland and the acute stage of subacute thyroiditis. The patient needs to go to a regular professional hospital for examination and treatment as soon as possible, in order to understand the condition more accurately and find the most suitable treatment for the patient as soon as possible. (a) History and physical examination The lymph nodes in the neck must be examined at the same time, and attention must be paid to distinguish whether the neck swelling originates from the thyroid gland. (This test should be a routine diagnostic tool for the thyroid gland. 131I and 99mTc radionuclides are available and the nodules can be classified into four categories according to the absorption function of the thyroid gland: 1. Hot nodules have a higher concentration of radionuclides in the thyroid nodule area than in the surrounding tissues and are most often seen in follicular adenomas or adenocarcinomas or toxic adenomas. 2. 2. Warm nodules are most often seen in adenomas, nodular goiter, Hashimoto’s disease, and recovery from subacute thyroiditis. 3. Cool nodules are usually seen in undifferentiated thyroid cancer, medullary carcinoma, cystic changes of the thyroid gland, and the acute stage of subacute thyroiditis. 4.Cold nodules are often thyroid cancer, but not absolutely. (C) Ultrasonography To detect the morphology, size, number and location of thyroid masses in relation to the carotid sheath; to determine whether the masses are cystic or solid; to clarify the condition of cervical lymph nodes; and as a means of localization for puncture examination. (iv) X-ray, CT and MRI examination The frontal and lateral cervical radiographs can understand the scope of tumor, different calcification images and the relationship with trachea and esophagus; CT and MRI examination can clearly show the size, morphology and the relationship with trachea, esophagus, blood vessels and even nerves of thyroid tumor, fully clarify the invasion scope of cancer and provide scientific basis for surgery. (E) Fine needle aspiration cytology examination Advantages: simple; no anesthesia (children can also receive it); no risk of bleeding and metastasis of cancer cells; high positive rate, very few false positives, false negative rate about 10%. (f) Laboratory tests are performed to check whether there are abnormalities in thyroid function and to help clarify the nature of thyroid swelling. Commonly used are: T3, T4, TSH, FT3, FT4, TGA, MCA, plasma calcitonin, ESR, etc.