I. Thyroid nodule onset A thyroid nodule is a mass of one or more abnormal tissue structures in the thyroid gland due to various causes. The incidence of palpable nodules increases with age, reaching 5% after age 50. However, autopsy, surgical exploration, and ultrasonography have a higher detection rate of up to 50%. The incidence is four times higher in women than in men, with the highest incidence after the age of 50. New nodules generally occur at 0.1% per year since early childhood and 2% per year after irradiation. The vast majority of thyroid nodules are benign, with malignancy accounting for 5-15%. There is no difference in the risk of malignancy between multiple nodules and a single nodule. Thyroid cancer is the fastest growing solid cancer, with incidence increasing by 6.2% per year (US data), and 5-15% of thyroid nodules are cancerous! The increased rate of early diagnosis and treatment is the most important reason why the mortality rate has not increased in parallel! Emphasis on the diagnosis and follow-up of thyroid nodules facilitates early detection. Ultrasonography and FNA are the predominant preoperative diagnostic methods. II. Fine needle aspiration biopsy of the thyroid gland Fine needle aspiration biopsy (FNA) of the thyroid gland is the only method to determine the pathological nature of nodules before surgery. FNA is the most critical part of the differential diagnosis process for thyroid nodules in many foreign medical centers and is considered the main primary screening tool for the diagnosis of thyroid nodules, with a diagnostic compliance rate of more than 80% and a confirmation rate of up to 90% as reported overseas. In addition, it has a high specificity in diagnosing chronic thyroiditis and subacute thyroiditis. Nowadays, it is commonly used in clinical practice to perform fine needle aspiration biopsy of the thyroid gland as follows: the patient is placed in a sitting or supine position, the neck is fully extended to reveal the puncture site, a fine needle of 7 to 8 gauge is used, the operator punctures the thyroid lesion with a fine needle with a 10 ml syringe, aspirates the tissue fluid with negative pressure, once the material is seen in the needle, the negative pressure is immediately removed and the needle is withdrawn, the aspirated tissue fluid is applied to a clean The aspirated tissue fluid is applied to a clean glass slide and subsequently quickly fixed in 95% alcohol for staining and cytological examination. Ultrasound-guided FNA improves the accuracy, especially for multiple nodules or nodules less than 1 cm in diameter. This method has few complications, allows repeated punctures, and is popular with patients. The use of fine needle aspiration biopsy of the thyroid has led to a significant reduction in the number of patients with surgically treated thyroid masses, as well as a significant increase in the malignancy rate for elective thyroid surgery. The correct rate of fine needle aspiration biopsy of the thyroid gland is about 85%, which is a good method for morphological diagnosis of the thyroid gland. the sensitivity, specificity, and accuracy of FNA are affected by many factors such as puncture technique, sampling site, staining method, and diagnostic experience. Without skilled puncture technique and rich experience in cytopathological diagnosis, the sensitivity, specificity and accuracy of FNA are difficult to meet clinical requirements.