Thyroid nodules and thyroid cancer are frequent and common diseases of the endocrine system: the prevalence of thyroid nodules in the general population is 3-7% on palpation and 20-76% on high-resolution ultrasonography. The prevalence of thyroid cancer in thyroid nodules is 5-15%. The diagnosis and treatment of thyroid nodules and thyroid cancer involves several clinical disciplines such as endocrinology, head and neck surgery, general surgery, and nuclear medicine, and is a typical interdisciplinary disease. The vast majority of patients with thyroid nodules have no clinical symptoms and are often detected by physical examination or by their own occasional touch. Thyroid nodules are classified into benign and malignant, with benign accounting for most of them. Depending on the cause of nodules, they can be classified as: nodular goiter, inflammatory nodules, toxic nodular goiter, thyroid cyst, benign thyroid adenoma and thyroid cancer. Patients are particularly concerned about whether thyroid nodules are malignant. Since benign and malignant thyroid nodules do not have characteristic clinical manifestations, a variety of indicators need to be considered in the differential diagnosis. Clinical evidence suggesting malignant thyroid nodules include: (1) age less than 20 years or more than 70 years; (2) family history of thyroid cancer; (3) history of neck radiation exposure during childhood; (4) male; (5) nodules growing rapidly and more than 2 cm in diameter; (6) with persistent hoarseness, dysphonia, dysphagia and dyspnea; (7) nodules with hard texture, irregular surface or fixed nodules; (8) with enlarged lymph nodes in the neck The nodule is hard, regular or fixed. Clinical evidence of benign thyroid nodules includes: (1) clinical manifestations of hypo- or hyperthyroidism; (2) family history of benign thyroid disease; and (3) pain or pressure in the thyroid nodule. Benign nodules are caused by nodular goiter, benign thyroid adenoma, cysts (degenerative adenoma and old hemorrhage with cystic changes, congenital thyroglossal cyst), acute suppurative thyroiditis, subacute thyroiditis, and Hashimoto’s thyroiditis. Ancillary tests are important in identifying the benignity and malignancy of thyroid nodules: the main ones are as follows. 1. Nuclear imaging of the thyroid gland can evaluate the function of the nodule and is of great value in determining the nature of the nodule. The majority (85-90%) of thyroid nodules are found to be non-functional cool or cold nodules, of which about 10-20% are malignant, while 10-15% are found to be functional warm and hot nodules, of which only 1% are malignant. The thyroid nuclear imaging has particular diagnostic value for autonomous high-functioning adenomas of the thyroid gland, which are long manifested as hot nodules, and normal thyroid images are suppressed and do not appear. 2. Evidence of malignant nodules suggested by ultrasonography: (1) irregular thyroid nodules with unclear borders, solid or cystic, (2) tiny calcifications within the nodules, and (3) abundant blood flow within the nodules. All three suggest a high specificity for malignant lesions, but one feature alone is not sufficient to diagnose malignancy. Nodules with enlarged lymph nodes in the neck also suggest malignant nodules. 3. Laboratory tests: All patients with thyroid nodules should have nail function. Most patients with malignant thyroid tumors have normal thyroid function; thyroid nodules caused by Hashimoto’s thyroiditis have elevated serum thyroid peroxidase antibodies (TPOAb) and thyroglobulin antibodies (TgAb), and elevated TSH. Significantly elevated serum calcitonin suggests medullary carcinoma of the thyroid nodule. 4. Fine needle aspiration cytology is the most reliable and valuable diagnostic method to distinguish benign and malignant nodules, and its results have 90% compliance with surgical pathology. Treatment of nodules: Thyroid cancer: total or near total thyroidectomy, postoperative treatment with 131 iodine to remove residual thyroid tissue and thyroid hormone suppression. The majority of patients with benign lesions do not require treatment, and follow-up is the main tool, requiring review every 6-12 months. A small number of benign lesions require oral eugenol therapy, which may result in nodule reduction. However, it is important to note that long-term use can lead to osteoporosis and atrial fibrillation. Ultrasound-guided transdermal alcohol injection therapy can be considered for thyroid cysts or nodules combined with cystic changes. 131 iodine therapy is particularly indicated for autonomic high-functioning adenomas and toxic nodular goiters.