The diagnosis of thyroid cancer is valuable in the early stage. Any isolated thyroid nodule found should be clinically excluded from thyroid cancer. If the nodule is hard and uneven, with enlarged cervical lymph nodes, paralysis of the recurrent laryngeal nerve or previous history of neck reflexes, the possibility of cancer is high. Similarly, if one of the multiple nodules in the thyroid gland is particularly prominent and hard, thyroid cancer should be suspected. In addition, if the thyroid itself appears asymmetrically enlarged or hard nodules that are rapidly increasing in size or have become fixed, thyroid cancer should be considered as a possibility. When making a diagnosis, do not rely too much on the uneven surface and hard texture of the lump as a characteristic of thyroid cancer. Some thyroid cancer lumps can be soft, smooth, and mobile, which is not uncommon in papillary carcinoma K. On the contrary, heavily calcified thyroid carcinoma, nodular thyroid, and sclerosing thyroiditis have a harder texture and a granular surface, which can be easily misdiagnosed as thyroid cancer. It is obviously incomplete to consider all cystic lesions of thyroid nodules as benign. The rate of cystic lesions becoming malignant has been reported to be 1.4%, and the rate of cystic changes in thyroid cancer also increases as the nodules grow. A 131I or 99mTc thyroid scan can only reflect the morphology of the nodule and its uptake of isotope function, and cannot determine its nature. However, clinical data show that the likelihood of thyroid cancer increases sequentially in the scanned images of hot, warm, cool and cold nodules. If a nodule of 0.5 cm or more is detected on scan and if it loses its isotope uptake, thyroid cancer may be considered (the presence of cysts should be excluded by ultrasonography), but it should be noted that thyroid cancer K does not always present as a cold nodule. In addition, the deficit in isotope distribution is related to the size of the tumor, and sometimes the image of a tumor with reduced function can be masked by normal thyroid tissue. A small number of thyroid cancers show hot nodules. If the above tests cannot confirm the diagnosis, fine needle aspiration cytology is feasible and should be performed 1 day before surgery for a high diagnostic compliance rate. In 10% of cases, no further cellular classification can be made and surgical exploration is still required for histological examination. In medullary thyroid carcinoma, serum calcitonin measurement and calcium administration or pentagastrin stimulation test can be used to make the diagnosis. In some patients, the malignancy of thyroid cancer is higher, and the enlarged cervical lymph nodes first appear as metastatic cancer, while the primary thyroid cancer is not detected by the patient.