Papillary carcinoma accounts for about 70% of all adult thyroid cancers, while pediatric thyroid cancers are often papillary carcinomas. Papillary carcinoma is common in young and middle-aged women, most common in women aged 21-40. This type is well differentiated, slow growing, and has low malignancy. It has a tendency to occur multicentrically and may appear early with lymph node metastasis in the neck, so early detection and active treatment are required, and the prognosis is now better. 2.Follicular carcinoma accounts for about 15%, 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. 3.Undifferentiated carcinoma accounts for about 5%-10%, mostly seen in the elderly, with rapid development and high malignancy, and about 50% of them have lymph node metastasis in the neck, or invade the laryngeal nerve, trachea or esophagus, and often metastasize to distant places through blood transport. The prognosis is very poor, with an average survival of 3-6 months and a one-year survival rate of only 5%-10%. 4.Medullary carcinoma is rare. It occurs in parafollicular cells (C cells), which can secrete calcitonin. The cells are arranged in a nested or bundle shape without papillae or follicular structures, and there are amyloid deposits in the interstitium, which are undifferentiated, but their biological characteristics are different from those of undifferentiated carcinoma. It is moderately malignant and may have cervical lymph node metastasis and hematologic metastasis.