Category 4 thyroid nodules include some malignant nodules, and if they are not malignant Category 4 nodules may become malignant as early as a few months. The overall malignancy rate of thyroid nodules in category 4 is about 50%-70% and can be associated with faster progression, with malignancy occurring as early as about 3 months. Category 4 thyroid nodules are classified as 4a, 4b and 4c, with category 4c nodules having the highest likelihood of malignancy, reaching about 85%, category 4b having a malignancy rate of about 15%-85% and category 4a having a malignancy rate of about 2%-15%. Therefore, all thyroid nodules diagnosed as category 4 need to be treated surgically. If the imaging diagnosis of thyroid nodules is category 4, the puncture result is benign, and the patient has no desire for surgery, in this case the patient is advised to review the ultrasound once every 3 months. If the nodule changes during the follow-up process, prompt surgical removal is required.