1.What is well-differentiated thyroid cancer Thyroid cancer is the most common endocrine malignant tumor, accounting for 1.1% of all malignant tumors. The mortality rate of thyroid cancer is low, accounting for about 0.2% of all tumor deaths. The 5-year relative survival rate of thyroid cancer is reported to be 95% in the literature. There are four main types of thyroid cancer: ① papillary carcinoma: the most common type of thyroid cancer, accounting for about 60-80% of thyroid cancer. Follicular carcinoma: moderately malignant, mostly seen in middle-aged people, the lesion is single and the main metastasis is hematogenous, accounting for about 20% of thyroid carcinoma; ③ Undifferentiated carcinoma: highly malignant, metastasizing to cervical lymph nodes at an early stage and also to bone and lung via hematogenous metastasis, commonly seen in the elderly, with a low incidence, accounting for about 5% of thyroid carcinoma; ④ Medullary carcinoma: originated from parafollicular cells (C cells) of the thyroid gland, which can secrete a large amount of calcitonin. Medullary carcinoma: originates from parafollicular cells (C cells) of the thyroid gland and can secrete a large amount of calcitonin. It is a medium malignant carcinoma. Metastasis to cervical lymph nodes can occur at an early stage, and hematogenous metastasis can occur at an advanced stage, accounting for about 5-10% of thyroid cancer. Differentiated thyroid carcinoma (DTC) includes papillary carcinoma and follicular carcinoma. How to diagnose well-differentiated thyroid carcinoma (1) Medical history: Time of thyroid enlargement, growth rate, local symptoms (difficulty in swallowing, pain or voice change) and systemic symptoms, age, sex, place of birth, family history and history of neck radiation, etc. (2) Clinical manifestations: ①Most cases present as isolated solid nodules in the anterior cervical region in the early stage, without obvious pain, which can move up and down with swallowing. (2) On palpation, single nodule of thyroid gland is firm in texture and has obvious boundary compared with surrounding tissues; if cancer infiltration and invasion are more extensive, the boundary of the mass is unclear and mobility is reduced. ③If the mass is rapidly enlarging and infiltrating, it may produce various compression symptoms, such as tracheal stenosis, softening, dyspnea, hoarseness and Horner’s syndrome. ④If thyroid cancer is accompanied by regional lymph node metastasis, enlarged lymph nodes can be palpated at the anterior and posterior margins of sternocleidomastoid muscle in the lateral cervical region, which are tough, painless and moderately mobile. If cancer invades the trachea, airway obstruction, hemoptysis or hemorrhage may occur. Difficulty in swallowing may occur when the esophagus is involved. (6) Medullary carcinoma often has specific symptoms, such as diarrhea, palpitations, facial flushing and decreased calcium, or Cushing’s metabolic syndrome. (7) If thyroid cancer metastasizes to the lung, liver, bone or brain, the corresponding clinical manifestations may occur. (3) Ancillary examinations: ①B ultrasound shows solid nodules with strong irregular reflections and uneven internal echogenicity. (2) CT shows irregular hypo- or iso-density image of thyroid gland, and enhanced scan shows obvious necrosis, which can show the invasion of surrounding organs and tissues by nail cancer. ③MRI shows thyroid tumor and the relationship between tumor and trachea, esophagus and blood vessels and cervical lymph node metastasis. ④The neck photograph can understand the tracheal compression and displacement, and the characteristic calcification signs in some nail cancers are scattered cloudy and sandy calcification shadows. PET-CT examination can help to diagnose nail cancer by showing FDG image of thyroid swelling absorption and can also show systemic metastasis of thyroid cancer. (4) Others: Although laboratory tests are not significant for the diagnosis of thyroid cancer, they can help to diagnose it by analyzing and judging together with medical history, physical signs and imaging examinations. For example, elevated thyroglobulin (Tg) is meaningful for the diagnosis of differentiated thyroid cancer and postoperative recurrence of thyroid cancer; elevated serum calcitonin helps to diagnose medullary carcinoma, and if it is continuously increased, the diagnosis can be basically confirmed. Fine needle aspiration cytology is an accurate diagnostic method for clinical diagnosis of thyroid cancer, which can find tumor cells and confirm the diagnosis. Using ultrasound to guide the examination, the diagnostic accuracy can reach over 95%. The gradual change of cystic swelling aspirate to dark red is a characteristic of metastasis of papillary thyroid cancer. For difficult diagnosis, biopsy of excised tissue of thyroid swelling or biopsy of suspicious enlarged lymph nodes in the neck can be performed to clarify the diagnosis. 3.How to treat well-differentiated thyroid cancer The treatment of differentiated thyroid cancer has been a hot issue of debate in thyroid surgery. In the past, the treatment of differentiated nail cancer was habitually associated with histopathological staging, that is, the surgical approach and scope were considered according to the histopathological findings. With the continuous development of new drugs and improvement of surgical techniques in recent times, the treatment of thyroid cancer has, to some extent, no longer focused on histopathological factors, but has shifted to rely more on the clinical stage and TNM stage of thyroid cancer to decide the treatment plan and surgical approach. For example, there is no difference in the choice of surgical approach and scope for small tumor lesions in the early thyroid lobes, whether papillary or follicular carcinoma, or even in the radiological 131I treatment plan for both, because the treatment plan often depends on the behavior of the metastasis rather than the histology of the primary lesion. Although follicular carcinoma is typically an invasive carcinoma, many recent studies have shown that the occurrence of metastases is not consistent with the histological features and behavior of their primary lesions. Therefore, it has been proposed that the majority of patients with postoperative thyroid cancer can be treated with radioiodine without regard to pathological staging. Most of the literature reports prognostic factors for differentiated thyroid cancer: age, size of the primary tumor, extent of tumor infiltration, extent of surgery, extent of lymph node dissection, and tumor metastasis. Haigh suggests that only age, extrathyroidal infiltration and regional or distant metastases are associated with the extent of surgical resection and that tumor size is not an independent factor. prognostic indicators. Univariate analysis of tumor recurrence at follow-up showed that age, primary lesion size, local tumor infiltration, extent of surgery, lymph node metastasis and clearance, postoperative isotope 131I therapy, and postoperative external radiation therapy were significant prognostic indicators. The results of multifactorial analysis showed that only age, extent of tumor infiltration, extent of surgery and lymph node clearance were independent prognostic indicators. In fact, postoperative external radiation is now rarely used to treat differentiated nail cancer lesions. The necessity of postoperative 131I therapy is also controversial, and the summary results of the data from Mayo Clinical Institute in the United States show that 131I therapy should not necessarily be used as routine treatment, especially for patients in the low-risk group. As for the age and extent of tumor infiltration at the time of first surgery, it has long been recognized that this is reflected in the UICC/AJCC TNM staging. The opinion that regional lymph node metastasis does not affect prognosis is also accepted by many scholars. The most controversial issues are the size of the primary tumor and the extent of surgery. Treatment methods: ① Surgery: It is the most basic treatment method, and different scope of surgery is adopted according to different stages. TSH suppression therapy has no therapeutic effect on the formed cancer, but it can slow down its development. However, it has a preventive effect on the unformed tumors to a certain extent. Therefore, surgery to remove the primary lesion is the first priority, and only when the primary lesion is removed can suppressive therapy have better efficacy. (iii) Postoperative 131I internal radiation therapy (ablative therapy) for fractionated thyroid cancer: Some DTC, such as papillary, follicular, mixed papillary-follicular carcinoma, Hurthle cell carcinoma, especially follicular carcinoma, have significant iodine uptake and iodine concentration function in about 75%. Because of the powerful radioactive effect of nuclear iodine on normal thyroid and iodine-intake cancer cells, these thyroid cancers have good therapeutic efficacy, but only after at least decompensated surgery, i.e., as an adjuvant treatment for DTC. Depending on the purpose of treatment, nuclear iodine therapy can be divided into ablation therapy after thyroidectomy and internal irradiation therapy when metastases are found and no further surgery is possible.