Thyroid function tests: mainly thyroid stimulating hormone (TSH) measurement. highly functional hot nodules with reduced TSH are less likely to be malignant, so it is more important to treat their hyperthyroidism. thyroid nodules with normal or elevated TSH, and cold or warm nodules with reduced TSH should be further evaluated (e.g., puncture biopsy). 2. Nuclear scan: Isotope scan examination (ECT) with radioactive iodine or technetium is an important tool to determine the functional size of thyroid nodules. According to the American Thyroid Association, “ECT findings include highly functional (higher uptake than the surrounding normal thyroid tissue), equifunctional or warm nodules (same uptake as the surrounding tissue), or nonfunctional nodules (lower uptake than the surrounding thyroid tissue). High-functioning nodules have a low rate of malignancy, and nodules need to be evaluated if the patient has significant or subclinical hyperthyroidism. If serum TSH levels are high, nodules should be evaluated even if they are only at the highest limit of the reference value, as this is when nodules have a higher rate of malignancy”. However, ECT often cannot show nodules smaller than 1 cm or microscopic cancer, so ECT should not be used for such nodules. Ultrasound: Ultrasound is an important tool to detect thyroid nodules and determine their benignity and malignancy, and is the standard for determining the possibility of performing fine needle aspiration biopsy (FNA). The European and American guidelines mention the following indications for suspicion of malignancy on ultrasound: hypoechoic nodules, microcalcifications, abundant blood flow signals, poorly defined borders, nodule height greater than width, solid nodules, and halo absence. In China, nodule morphology, boundary, aspect ratio, peripheral halo, internal echogenicity, calcification, and cervical lymph nodes have been analyzed and evaluated, and compared with the postoperative pathological results, it was statistically concluded that nodule morphology, calcification, and internal echogenicity are more relevant in the differentiation of benign and malignant thyroid nodules, and this aspect can be observed (only for papillary carcinoma). Needle aspiration smear cytology: Needle aspiration biopsy includes both fine needle aspiration biopsy and coarse needle aspiration biopsy, the former is cytological examination and the latter is histological examination. For thyroid nodules with suspected malignant changes found by ultrasound, this method can be used to make a clear diagnosis. Currently, fine needle biopsy is generally performed with the patient lying supine in a cervical hyperextension position. Local anesthesia is desirable. The importance of multidirectional puncture is emphasized, and at least 6 punctures should be performed to ensure that adequate specimens are obtained. During puncture, fix the node with the middle finger of the left index finger, hold the syringe with the right hand, pump back the needle plug to generate negative pressure, while slowly pulling the needle outward by 2 mm, and then puncture again, repeat several times to stop aspiration after seeing cell debris inside the needle, remove the negative pressure, pull out the needle, disconnect the syringe, inhale several milliliters of air inside the syringe, attach the needle, and drain the specimen inside the needle onto the slide, requiring 1-2 drops of orange-red liquid with cell debris. Then smear the slide for examination.