Basic knowledge of thyroid gland and basic knowledge of thyroid tumor: What is thyroid gland? The thyroid gland is located in the neck below the thyroid cartilage, on both sides of the trachea, and is shaped like a butterfly, like a shield nail, so it is called the thyroid gland. The thyroid gland is divided into two lobes, the right and left, and the isthmus. The left and right lobes are located on both sides of the lower part of the larynx and the upper part of the organ. The upper end is from the midpoint of the thyroid cartilage, the lower end to the 6th tracheal cartilage ring, and sometimes to the superior sternal fossa or behind the sternum. The main functions of the thyroid gland: The thyroid gland has the function of synthesizing, storing and secreting thyroxine. Accelerate the effectiveness of oxygen utilization by cells throughout the body, accelerate the decomposition of proteins, carbohydrates and fats, increase the overall metabolism of the body, and increase heat production;? Promote human growth and development, mainly affecting the brain and long bones after birth. (a) What are the main benign thyroid tumors: Benign thyroid tumors are very common, and thyroid adenomas account for about 50% of the neck masses. When the tumor is large, it may cause breathing difficulty, swallowing difficulty, hoarseness and other symptoms due to compression of trachea, esophagus and nerves. When the tumor is combined with bleeding and rapidly increasing in size, it will produce local distension and pain. Because benign thyroid tumors may become malignant, thyroid adenoma is the most common benign thyroid tumor. The onset of the disease is insidious, with a neck lump being the main complaint, mostly asymptomatic. The nodules are mostly solitary, round or oval, often confined to one side of the gland, with a medium texture, smooth surface, no pressure pain, and moving up and down with swallowing. Thyroid adenoma may cause hyperthyroidism (incidence about 20%) and malignancy (incidence about 10%), so in principle, it should be removed early. Surgery: Generally, the affected side of the thyroid gland should be removed (including the adenoma), and the specimen must be examined immediately by frozen section to determine whether there is malignancy. Nodular goiter may be caused by a deficiency of iodine in the diet or a deficiency of the enzymes that synthesize thyroid hormones. Most nodules are multinodular, but a few are single nodules. The nodules can be treated conservatively, but surgery should be performed if they are large enough to produce symptoms of pressure (dyspnea, dysphagia or hoarseness), have a tendency to become malignant or are combined with symptoms of hyperthyroidism. （The most common malignant tumor of thyroid gland is thyroid cancer. 1. papillary carcinoma accounts for about 70% of all thyroid cancers in adults, while all thyroid cancers in children are often papillary carcinomas. The disease has a tendency to occur multicentrically and may appear early with lymph node metastasis in the neck. Follicular carcinoma accounts for about 15% of the cases, mostly seen in women around 50 years old. This type is fast developing, moderately malignant, and has the tendency to invade blood vessels. Cervical lymph node metastasis only accounts for 10%, so the prognosis is not as good as papillary carcinoma. Undifferentiated carcinoma (anaplastic thyroid carcinoma) accounts for about 5%-10%, mostly seen in elderly people, with rapid development and high malignancy, with an average survival of 3-6 months and a one-year survival rate of only 5%-10%. 4.Medullary thyroidcarcinoma is rare. It is moderately malignant and can have cervical lymph node metastasis and hematologic metastasis.