Thyroid tumors are divided into two categories: benign and malignant, benign including nodular goiter, thyroid adenoma, chronic thyroiditis and so on, while malignant can be divided into papillary carcinoma, follicular carcinoma, medullary carcinoma, undifferentiated carcinoma, lymphoma and so on according to the pathology. After surgical treatment, no matter benign or malignant tumors, they need regular follow-up and further treatment if necessary. The function of the thyroid gland is complex and wide-ranging, regulating the body’s metabolism mainly through the secretion of thyroxine. Either hyperfunction (hyperthyroidism) or hypothyroidism (hypothyroidism) can cause disorders in the body’s functions, resulting in corresponding symptoms, and in serious cases, even life-threatening. Surgical removal of a tumor, which necessarily includes some or all of the thyroid glands, will more or less affect the secretion of thyroxine, changing the body’s hormone levels, which in turn affects the body’s metabolism. If it exceeds the normal range, it may cause surgery-related changes in thyroid function, and most patients show secondary hypothyroidism or relative hypothyroidism compared with the preoperative period. Therefore, most patients require exogenous thyroxine supplementation after surgery, mainly through oral administration of thyroxine tablets or levothyroxine, to keep the body’s thyroxine level in the normal range. For nodular goiter and adenoma, the pathogenesis may be related to thyroid hormone deficiency (e.g., iodine deficiency and other factors) feedback causing overproduction of thyrotropin (TSH) to stimulate thyroid tissue proliferation. It may affect part or all of the thyroid gland. After removal of the tumor and diseased glands during surgery, oral supplementation with thyroxine adjusts thyroxine levels in the normal range on the one hand, and on the other hand, through exogenous thyroxine (T4), feedback inhibits the synthesis of TSH, which in turn reduces the chance of recurrence. Therefore, theoretically, all these patients should receive thyroxine therapy after surgery. Generally, after taking a certain dose of oral thyroxine tablets or levothyroxine regularly for a period of time (more than 1 month is preferred), the thyroxine level is basically stabilized, and blood tests for thyroid function are drawn, including T3 (triiodothyronine), T4 (thyroxine), FT3 (free triiodothyronine), FT4 (free thyroxine), TSH (thyrotropin), etc. The patient should be treated with a thyroid hormone therapy. The dose of oral medication is adjusted according to thyroid function and the patient’s symptoms. If adjustments are made, thyroid function should still be rechecked after a period of time until it is more satisfactory. It will be reviewed every six months to a year thereafter. For patients with chronic thyroiditis, chronic lymphocytic thyroiditis is the most common. This disease, also known as Hashimoto’s thyroiditis, is an autoimmune disease with an unknown pathogenesis. Patients often have antibodies against their own thyroid components, the most common of which are antithyroglobulin antibodies (TGA), antithyroid microsomal antibodies (TMA), and antibodies against the membranes, nuclei, and glial components of thyroid follicular cells. Serum tests for TGA and TMA are often significantly elevated. Some patients have combined thyroid cancer or lymphoma. Surgery is not the treatment of choice and is only considered in cases of combined thyroid nodules, not excepting malignancy or with symptoms of tracheal compression. Due to the effect of Hashimoto’s thyroiditis on thyroid function, patients may have mild hyperthyroidism in the early stages, followed by a slow decrease in thyroid function and eventually hypothyroidism. Therefore, regardless of whether surgery is performed or not, thyroid function should be closely monitored (in addition to T3, T4, FT3, FT4, TSH as mentioned above, TGA and TMA may also be included), and thyroxine supplementation or medications for hyperthyroidism, such as Tabazolol, should be taken if necessary. In addition thyroiditis also includes chronic fibrous thyroiditis, subacute thyroiditis, granulomatous thyroiditis, etc. The pathogenesis is unknown. If the tumor is large, it can be treated surgically. Postoperative thyroxine therapy is also applied. For the above benign thyroid diseases, recurrence still occurs in some patients after surgery. There are several diagnostic methods for thyroid disorders, but ultrasound remains the most sensitive and specific for the thyroid gland itself compared to CT, MRI or isotope scans. Therefore, the use of ultrasound is a cost-effective means of providing review for these patients. Physical examination remains the simplest and easiest method. During follow-up, an experienced surgeon can promptly detect recurrent tumors and even estimate the nature of recurrent tumors by routine physical examination. Even if a localized thyroid tumor is found to be recurrent, reoperation is not always necessary. Only for recurrent tumors that are large (usually over 2~3cm in diameter), not excluding the possibility of malignancy (especially for elderly patients with nodular thyroid, a few of which may develop malignancy, or even intermediate into undifferentiated carcinoma), or with obvious symptoms, such as compression of the trachea and esophagus, etc., will reoperation be considered. There are four common pathological classifications of thyroid cancer: papillary carcinoma is the most common, accounting for about 70~80%, follicular carcinoma is the second most common, accounting for about 10~20%, medullary carcinoma accounts for about 3~8%, and undifferentiated carcinoma accounts for about 3~5%. The first two types of tumors are collectively called differentiated thyroid carcinoma, which has a better prognosis, with a 5-year survival rate of 80-95% and a 10-year survival rate of 50-90%. However, the prognosis of patients is related to their age. If the age is more than 45 years old, the survival rate is lower than that below 45 years old. Medullary carcinoma is between differentiated and undifferentiated type, with 5-year survival rate of about 80% and 10-year survival rate of 70-75%. Undifferentiated carcinoma includes large cell carcinoma, small cell carcinoma, squamous cell carcinoma, sarcoma, carcinosarcoma, fibrosarcoma, malignant fibrous histiocytoma, as well as papillary carcinoma and follicular carcinoma which are poorly differentiated, etc. The prognosis of undifferentiated carcinoma is extremely poor, and most of the patients die within 1 year, and the survival rate of 5 years is about 5~15%. Surgical treatment for differentiated thyroid carcinoma and medullary carcinoma generally includes resection of thyroid lobe + isthmus on the diseased side, total thyroidectomy if necessary (including some patients with high risk of recurrence), ipsilateral tracheo-esophageal sulcus lymph node dissection, cervical lymph node dissection if lymph node metastases are found on one side or both sides, and if there are mediastinal lymph node metastases, mediastinal lymph node dissection is performed at the same time, and if necessary, splitting of the sternum is performed. As for the treatment of undifferentiated carcinoma, if the tumor is small, it can refer to the above treatment. If the tumor is large, or even invades into the surrounding tissues, such as trachea, esophagus, larynx, blood vessels, etc., even if the surgery can be basically clean, the tumor may recur, metastasize, or even die soon. Therefore, palliative resection is recommended to avoid sacrificing vital organ functions. For patients who may invade the trachea or have difficulty in breathing, tracheotomy should be performed prophylactically or electively to maintain the smoothness of the airway. Postoperatively, patients with undifferentiated cancer should be routinely treated with radiation therapy, supplemented with chemotherapy if necessary, to slow down or control tumor recurrence. For patients with thyroid cancer, postoperative review and further treatment should include: regulation of thyroid function, timely detection and treatment of tumor recurrence and metastasis, and management of postoperative complications. After surgical removal of one side or the whole thyroid gland, thyroxine should be supplemented routinely to maintain the thyroid function as normal as possible. (Methods and monitoring are the same as those for benign thyroid tumors). For differentiated thyroid cancer, long-term supplementation of thyroxine can inhibit the secretion of TSH, reduce the possibility of tumor recurrence, and significantly improve the prognosis of patients. Therefore, the level of TSH should be paid close attention to during follow-up, and it is better to maintain it under normal value, while other indicators are within normal range. After thyroid cancer surgery, regular review should be conducted to detect possible local recurrence or metastasis of the tumor, including neck and upper mediastinal lymph node metastasis and distant metastasis, such as metastasis in lungs, bones, brain and other parts of the body. It is generally recommended to review regularly at 3 months, 6 months and 1 year after surgery, and every 6 months after 1 year. The examination methods include routine physical examination, thyroid and neck ultrasound, CT, MRI, isotope examination, chest radiographs, etc. If suspicious nodules are found, cytology or pathology examination will be performed to clarify the nature if necessary. Some serological examinations are also helpful, for example, for total thyroidectomy for differentiated thyroid cancer, obvious elevation of TG (thyroglobulin) suggests the possibility of tumor recurrence; for medullary carcinoma patients, substantial elevation of serum procalcitonin level also suggests tumor recurrence or metastasis. If the examination finds that the tumor has local recurrence or lymph node metastasis in the neck or upper mediastinum, most patients can still achieve radical treatment through reoperation. For differentiated thyroid cancer, if lung metastasis occurs, all the residual thyroid glands can be removed, and after removing all the metastatic lymph nodes, 131I isotope therapy can be performed, which can also achieve better curative effect. For distant metastases in bone, brain and other parts of the body, sometimes the metastatic foci can be resected first, and then isotope therapy can be performed. If surgical resection is not possible, the treatment is the same as lung metastasis. It should be reminded that radiotherapy and chemotherapy are not recommended for differentiated thyroid cancer and medullary carcinoma that can be removed by surgery. Because radiotherapy and chemotherapy cannot bring higher cure rate and control rate, but on the contrary will bring more side effects and complications. Only for patients with only a small amount of residual tumor after major resection, postoperative radiotherapy can improve the control rate and prognosis. For patients with undifferentiated thyroid cancer, tumor recurrence or metastasis may occur in a short period of time, so the interval of follow-up should be narrowed, such as once every 1 month. Once recurrence or metastasis is detected, it suggests a poor prognosis and the tumor tends to grow rapidly. Most patients lose the chance of reoperation and can only be managed symptomatically or controlled with radiotherapy or chemotherapy, etc. Surgery may be able to do little more than a tracheotomy or tracheostomy to address ventilation and a gastrostomy to address feeding. After thyroidectomy and cervical lymph node dissection, some patients may have surgery-related complications, such as hoarseness and choking on food due to damage to the recurrent laryngeal nerve, hypocalcemia due to damage to the parathyroid glands, numbness or even convulsions in the limbs and face, and corresponding dysfunction due to damage to the cervical nerves. Patients do not return to normal when they are discharged from the hospital, and they need to be observed and advised in the follow-up process to assist in the recovery of function. Especially after total thyroidectomy, the parathyroid glands are damaged, and some patients have hypocalcemia, which should be supplemented with calcium in a timely manner, including oral or intravenous calcium infusion, in order to reach or approach the normal blood calcium level as much as possible. Blood calcium and parathyroid hormone levels should be rechecked regularly after discharge and calcium supplementation should be continued. For laryngeal recurrent nerve and other nerve injuries in the neck, patients should be instructed to carry out functional training in order to restore or compensate for the damaged nerve function as soon as possible. For primary lymphoma of thyroid gland, there is a trend of increase at present, after diagnosis, comprehensive treatment of lymphoma should be carried out in time, including radiotherapy, chemotherapy, etc., which can also get better therapeutic effect.