Thyroid cancer is the most common malignant tumor of the thyroid gland, accounting for about 1% of all malignant tumors in the body. Except for medullary carcinoma, the vast majority of thyroid cancers originate from follicular epithelial cells. The following types of thyroid cancer can be seen under ultrasound: 1. Irregular shape of the mass: unclear border or incomplete halo, uneven hypoechoic inside, mostly with sandy strong echogenic calcification. This is the “parenchymal inhomogeneous hypoechoic dark area type”. It is the most common type of thyroid cancer and is relatively easy to diagnose. Most of them are papillary carcinoma. 2. The mass has clear borders, neat shape and hypoechoic interior, and the posterior echogenicity may be reduced. This is the “substantial attenuated dark area type”. It is commonly seen in follicular adenocarcinoma and medullary carcinoma. 3.Mass with clear boundary and envelope: uniform or uneven internal echogenicity (may be accompanied by arcuate or patchy strong echogenic coarse calcification) or mixed liquid and solid echogenicity. That is, “adenoma type”. 4.The boundary of the mass is clear or unclear: the interior is liquid or mixed dark area. That is, “cystic change”. However, it should be pointed out that: liquid dark areas or liquid-solid mixed echogenicity are not always caused by benign lesions; clear borders, envelope, and more uniform internal echogenicity are not all benign lesions; uneven internal echogenicity of the mass with curved or patchy strong echogenic coarse calcification can exist in both cancerous nodules and recurrently hyperplastic nodular goiter nodules. Therefore, ultrasound alone cannot be used as an absolute basis for differentiating between benign and malignant nodules.