Thyroid cancer is the most common malignant tumor of the thyroid gland, accounting for about 1% of all malignant tumors in the body. Except for medullary carcinoma, the vast majority of thyroid cancers originate from follicular epithelial cells. What are the ways of spreading and metastasis of thyroid cancer? 1.Internal spread of thyroid cancer: There is a rich lymphatic duct network in the thyroid gland, and tumor cells can spread along the lymphatic duct network in the thyroid gland. 2.External expansion of thyroid cancer: Thyroid cancer can break through the thyroid envelope and further invade the surrounding tissues and organs, such as trachea, esophagus, laryngeal nerve, thyroid cartilage and blood vessels. 3.Lymph node metastasis: It can often metastasize to the lymph nodes in the upper and middle groups of the deep neck, with the middle and lower groups being common. 4.Distant metastasis: Thyroid cancer can often metastasize distantly, with lung metastasis being the most common, followed by bone metastasis.