1. Serological tests (TT3, TT4, FT3, FT4, TSH, TPOAb, TGAb, for short: seven tests of thyroid function). The presence of hyperthyroidism or decreased TSH indicates autonomic functional thyroid adenoma, nodule or toxic multinodular goiter. Patients with medullary thyroid cancer have elevated serum calcitonin levels. Normal or abnormal thyroid function may indicate the possibility of thyroid cancer. Ultrasound examination of thyroid gland may show solid, cystic or mixed nodules, while a single solid nodule has a higher chance of malignancy and a mixed nodule also has the possibility of malignancy, while a simple cystic nodule has less chance of malignancy. If the nodule is accompanied by calcification, 10% may be malignant, with sand-like malignancy being more likely. According to the uptake of radionuclide by the nodules, they are classified as “hot nodules” and “cold nodules”. “Hot nodules are functionally autonomous thyroid nodules and are almost always benign. “In addition, if there is bleeding or cystic changes in the nodule, it may also be a “cold nodule”. 4. Small or sand-like calcifications on the CT or MR nodules of the thyroid gland may be the sand bodies of papillary carcinoma. Large, irregular calcifications can be seen in degenerative nodular goiter or thyroid cancer. If infiltration or distortion is seen in the tracheal image, it is suggestive of a malignant lesion. It can also diagnose retrosternal goiter; if it is a malignant tumor, clarifying the invasion of important tissues such as neck vessels, trachea and esophagus is an important guideline for surgery. 5.Fine needle aspiration cytology reduces unnecessary thyroid surgery, improves the detection rate of intraoperative malignant tumors, and reduces treatment-related costs. The accuracy rate of fine needle aspiration cytology examination reaches 70% to 90%, which is related to the experience of aspiration and cytology diagnosis.