I. Overview A thyroid nodule is a mass or masses of abnormal tissue structure in the thyroid gland due to various causes. Thyroid nodules present differently in different tests. For example, a thyroid nodule found by palpation is a mass that is palpated in the thyroid region. A thyroid nodule detected by ultrasound of the thyroid is an area of focal echogenic abnormality. The results of the two tests are sometimes inconsistent, such as when a thyroid mass is palpated on examination but no nodule is found on thyroid ultrasound, or when a thyroid nodule is not palpated on examination and a thyroid nodule is found on thyroid ultrasound. Thyroid nodules are very common. The prevalence of thyroid nodules in the general population is 3% to 7% on palpation, while the prevalence of thyroid nodules on high-resolution ultrasound is 20% to 70%. Most thyroid nodules are positive, and malignant nodules account for only about 5% of thyroid nodules. The key to the diagnosis and treatment of thyroid nodules is to identify benign and malignant. 1. Proliferative nodular goiter: high or low iodine, consumption of goiter-causing substances, consumption of goiter-causing drugs or defective thyroid hormone synthesis enzymes, etc. 2. Neoplastic nodules: benign thyroid adenoma, papillary thyroid carcinoma, follicular cell carcinoma, Hürthle cell carcinoma, medullary thyroid carcinoma, undifferentiated carcinoma, lymphoma, and other follicular cell and non-follicular cell malignancies of the thyroid gland, as well as metastatic carcinoma. 3.Cysts: nodular goiter, degenerative adenoma and old hemorrhage with cystic changes, cystic changes of thyroid cancer, congenital thyroglossal cysts and cysts due to remnants of the fourth gill slit. 4. Inflammatory nodules: acute suppurative thyroiditis, subacute thyroiditis, and chronic lymphocytic thyroiditis can all appear in the form of nodules. In rare cases, thyroid nodules are due to tuberculosis or syphilis. Clinical manifestations Most patients with thyroid nodules have no clinical symptoms and are often detected by physical examination or by their own touch or imaging. When the nodules compress the surrounding tissues, corresponding clinical manifestations may appear, such as hoarseness, breath-holding, and difficulty in swallowing. When combined with hyperthyroidism, corresponding clinical manifestations of hyperthyroidism may appear, such as palpitations, excessive sweating, hand tremors, etc. A detailed history taking and a thorough physical examination are important to assess the nature of the thyroid nodule. The main points of history taking are the patient’s age, gender, history of head and neck radiotherapy, size and rate of change and growth of the nodule, presence of local symptoms, presence of hyperthyroidism and hypothyroidism, presence of thyroid tumors, medullary thyroid carcinoma or multiple endocrine adenomatosis type 2 (MEN2), familial polyposis, Cowden’s disease and Gardner’s syndrome. A history of familial diseases such as Cowden’s disease and Gardner’s syndrome. The physical examination focuses on the number, size, texture, mobility, presence of pressure pain, and presence of enlarged lymph nodes in the neck of the nodule. Clinical evidence of malignant thyroid nodules include: (1) history of radiotherapy of the neck; (2) family history of medullary thyroid carcinoma or MEN2; (3) age less than 20 years or more than 70 years; (4) male; (5) rapidly growing nodules with a diameter of more than 2 cm; (6) persistent hoarseness, dysphonia, dysphagia and dyspnea; (7) hard, irregular and fixed nodules; (8) enlarged lymph nodes in the neck. enlargement. 1. Serum TSH and thyroid hormone: All patients with thyroid nodules should have serum TSH and thyroid hormone levels measured. The majority of patients with malignant thyroid tumors have normal thyroid function. If serum TSH is decreased and thyroid hormone is increased, this is indicative of a high functioning nodule. These nodules are almost always benign. 2. Thyroid autoantibodies: Serum TPOAb and TgAb levels are one of the golden indicators for detecting Hashimoto’s thyroiditis. More than 85% of patients with Hashimoto’s thyroiditis have elevated levels of serum anti-thyroid antibodies. However, a small number of patients with Hashimoto’s thyroiditis may have a combination of papillary thyroid cancer or thyroid lymphoma. 3. Measurement of thyroglobulin (Tg) levels: Serum Tg is not helpful in identifying the nature of the nodule. 4.Measurement of serum calcitonin level: A significantly elevated serum calcitonin level suggests medullary thyroid nodules. Those with family history of medullary thyroid carcinoma or multiple endocrine adenomatosis should have their serum calcitonin levels measured in the basal or stimulated state. 5.Thyroid ultrasonography: High-definition thyroid ultrasonography is the most sensitive method to evaluate thyroid nodules. It can be used not only to discriminate the nature of nodules, but also for ultrasound-guided thyroid FANC.