The description of thyroid nodule category 3 and 4 is mainly the result of thyroid ultrasound on the thyroid nodule a kind of image description, the difference between thyroid nodule category 3 and 4 is different in benign and malignant, thyroid nodule category 3 are basically benign nodules, while thyroid nodule category 4 are malignant tendency. Class 4 is divided into three classes: a, b, and c. Class a nodules are about 20% malignant, class b nodules are about 50% malignant, and class c nodules have a malignant likelihood of 70-80%. Any thyroid nodule that reaches category 4 or higher needs to be closely followed up and, if necessary, a puncture biopsy of the thyroid nodule should be considered. Thyroid nodules in category 3 can be left alone because they are benign, but those in category 4 should be followed closely because of the possibility of malignancy.