Thyroid carcinoma 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 majority of thyroid carcinomas originate from follicular epithelial cells. Papillary carcinoma accounts for about 60% of thyroid cancer in adults and all thyroid cancer in children. It is mostly seen in the age of 30 to 45. It is less malignant, about 80% of tumors are multicentric, and about 1/3 involve bilateral thyroid gland. This is important for planning treatment. Cervical lymph node metastasis appears early, but the prognosis is better. Follicular adenocarcinoma accounts for about 20% and is common in middle-aged people around 50 years old. Cervical lymph node invasion only accounts for 10%, so the prognosis of patients is not as good as papillary carcinoma. 3.Undifferentiated carcinoma accounts for about 15%, mostly seen in elderly people around 70 years old. It develops rapidly and about so% of them have cervical lymph node metastasis at early stage and are highly malignant. In addition to invading trachea and/or laryngeal nerve or esophagus, it can also metastasize to lung and bone distantly through blood transport. The prognosis is very poor. The average survival time is 3-6 months, and the one-year survival rate is only 5%-15%. 4.Medullary carcinoma accounts for only 7%. The cells are nested or cystic in shape, without papillae or follicular structures, and are undifferentiated; there are amyloid deposits in the tumor. It may have both cervical lymph node invasion and hematogenous metastasis. The prognosis is not as good as papillary carcinoma, but better than undifferentiated carcinoma. In conclusion, the biological characteristics, clinical manifestations, diagnosis, treatment and prognosis of different pathological types of thyroid cancer are different. Clinical manifestations A lump found in the thyroid gland with hard and fixed texture and uneven surface is a common manifestation of all types of cancer. The gland has little up and down mobility during swallowing. Undifferentiated carcinoma may show the above symptoms within a short period of time. In addition to the obvious growth of the mass, it also has the characteristic of invading the surrounding tissues. In late stage, it may produce hoarseness, difficulty in breathing and swallowing, sympathetic nerve compression causing Horn-er syndrome and invasion of cervical plexus causing pain in ear, occiput and shoulder and local lymph node and distant organ metastasis. Cervical lymph node metastasis occurs earlier in undifferentiated carcinoma. In some patients, the possibility of thyroid cancer should be thought of when the metastases are found in patients with inconspicuous thyroid masses. Patients with medullary carcinoma should exclude the possibility of multiple endocrine adenoma syndrome type II (MEN-II). In case of combined family history and presence of diarrhea, facial flushing and low blood calcium, care should be taken not to miss the diagnosis. The diagnosis is mainly based on clinical manifestations. If the thyroid mass is hard and fixed, if the cervical lymph nodes are enlarged, or if there are symptoms of pressure, or if the thyroid mass has existed for many years and rapidly increased in size within a short period of time, thyroid cancer should be suspected. Attention should be paid to differentiate it from chronic lymphocytic thyroiditis, and fine needle aspiration cytology may help in the diagnosis. In addition, serum calcitonin assay can assist in the diagnosis of medullary carcinoma.