1. Neck ultrasound: The preferred method for diagnosing the nature of thyroid nodules. Experienced physicians can determine the nature of thyroid nodules by ultrasound with an accuracy rate of 90%. Therefore, patients with thyroid nodules found by palpation can have an ultrasound examination to further clarify the diagnosis. Benign nodular goiters are most common, and most ultrasound images show multiple, inhomogeneous echogenicity. Cysts generally appear hypoechoic and may appear as light spots if there are bleeding spots within the capsule. Those with eggshell calcification may have significant strong echogenicity. Nodular goiter combined with adenomatous hyperplasia may show a solid component on sonogram. There is usually no blood flow within the mass or there is encircling blood flow. For malignant thyroid nodules, papillary thyroid carcinoma is the most common. The typical ultrasound image shows a hypoechoic nodule that has the following characteristics: indistinct margins, uneven echogenicity within the nodule, irregular disorganized blood flow in the center of the nodule, and multiple punctate strong echogenicity or gritty calcifications. The more the above symptoms are met, the higher the possibility of thyroid cancer. Especially, the presence of multiple punctate strong echogenicity or sandy calcifications is almost the signature ultrasound feature of papillary thyroid cancer. 2.Fine needle aspiration cytology: The advantage of this test is that it can obtain cytological or pathological diagnosis, and the accuracy rate of differentiating benign and malignant nodules is as high as 95%. The disadvantage is that this test is invasive and it is not easy to diagnose follicular adenocarcinoma. For chronic lymphocytic thyroiditis, serum tests for thyroglobulin antibodies (TGA) or thyroid microsomal antibodies (TMA) may be significantly higher. Thyroglobulin (TG) measurement cannot be used to differentiate between benign and malignant nodules because TG can be elevated in benign thyroid tumors and nodular goiter, and TG levels can also be elevated when the thyroid gland is acutely damaged by surgery, infection, or radiation. The serum calcitonin test is specific for the diagnosis of medullary thyroid cancer. 4.Thyroid radionuclide scan: With the increasing level of ultrasonic diagnosis technology, thyroid scan has been rarely used. Its findings usually show cold nodules, warm nodules and hot nodules. There are 18.4% to 54.5% of single cold thyroid nodules are thyroid cancer, but 4% to 7% of hot nodules are also cancerous. Therefore, this test is difficult to distinguish the nature of thyroid nodules and has been gradually replaced by ultrasound.