The thyroid gland is located in the middle of the front of the neck and is shaped like a recluse nail, hence the name thyroid. It moves up and down with the trachea when swallowing. The thyroid gland is surrounded by many important nerves and blood vessels, and damage to the recurrent laryngeal nerve will result in hoarseness. The thyroid gland has many important physiological functions. It secretes the thyroid gland to promote the body’s metabolism, but too much secretion can lead to hyperthyroidism, too little secretion can lead to hypothyroidism, and a lack of it in children can lead to mental retardation. Ultrasonographic manifestations of thyroid cancer: 1. Number of nodules: Most of them are single, and a few of them are multiple. However, with the use of high-frequency ultrasound, many tiny nodules can be detected, therefore, single or multiple nodules are less and less valuable in determining the benignity and malignancy. 2. Internal hypoechogenicity of nodules: Most of them are hypoechoic and few are isoechoic or hyperechoic. However, the internal hypoechoic lesion does not mean that it is malignant, because 90% of thyroid nodules can be hypoechoic; in addition, the internal echogenicity of malignant nodules is more than “uneven” and the posterior echogenicity is diminished or disappears, which can be distinguished from the “uniform hypoechogenicity” of benign nodules. This can be distinguished from the “homogeneous hypoechogenicity” of benign nodules. 3, the longitudinal ratio of the nodule: the longitudinal ratio is close to 1, the peripheral boundary is unclear, the shape is not regular, or it becomes crab foot-like, and there is no or no complete acoustic halo (dark ring) around the mass, etc. should be considered as malignant possibility. 4, the growth rate of nodules: faster growth rate (different time ultrasound comparison), rapid increase in nodules within a short period of time, after excluding intracapsular bleeding, should be highly suspected of malignancy. 5, with gravel-like calcification: calcification foci are generally divided into microcalcification, coarse calcification, and circular calcification. At present, scholars at home and abroad generally believe that microcalcifications are the most specific index for diagnosing thyroid cancer, especially for papillary carcinoma, which can reach over 90%. In addition, in young patients (less than 40 years old), if calcification is found in a single nodule, the possibility of malignancy increases 4 times. 6. Lymph node metastasis: The ratio of long to short diameter of metastatic lymph nodes in thyroid cancer is less than 1.5 in most cases, with hypoechoic and uneven internal echogenicity. The ipsilateral internal jugular vein and carotid artery, trachea are involved or adhered to the anterior cervical muscle. 7. Color Doppler flow imaging of nodules rich in blood vessels: color Doppler flow imaging of malignant nodules has a blood flow distribution or internal linear branching blood flow. In malignant nodules, due to high metabolism and rapid tumor tissue appreciation, the neovascularization lacks smooth muscle and has a thin wall. High-velocity, low-resistance blood flow with peak systolic velocity of 70 cm/s or more is seen. Therefore, if the signal of high-velocity blood flow in thyroid nodules is greater than 70 cm/s, the possibility of cancer should be considered. In addition, thyroid hormone (TSH) should be checked in patients with thyroid nodules. For those with TSH below normal, thyroid ECT (with 99mTcO4 or 123I) should be done to exclude high-functioning thyroid adenomas. The differentiation of benign and malignant thyroid nodules is most important in clinical practice. Fine needle aspiration cytology is an important basis for differentiating benign and malignant thyroid nodules.