I. The following factors need to be alerted to the possibility of thyroid cancer: ① hard, fixed nodules with irregular shape; ② rapid growth of nodules; ③ hoarseness, difficulty in swallowing and breathing difficulties; ④ enlarged lymph nodes in the neck; ⑤ history of treatment with neck radiography; ⑥ age <20 years or >70 years; ⑦ familial thyroid disease, thyroid cancer, familial (vii) History of familial thyroid disease, thyroid cancer, familial polyposis, and other familial diseases. Ultrasound shows the following signs to alert the possibility of malignancy: ① microcalcifications; ② irregular nodule margins or microfollicular margins without halo; ③ disturbance of blood flow in the nodule (rich vascularity, disorganized distribution, curvature and branching of blood vessels); ④ extrathyroidal invasion or enlargement of lymph nodes in the neck, loss of lymph node gate structure, cystic changes or microcalcifications and disturbance of blood flow in the lymph nodes; ⑤ anteroposterior diameter of the lesion is larger than the transverse diameter