There are several types of thyroid cancer under ultrasound: ① Irregular shape of the mass, unclear borders or incomplete halo, heterogeneous 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. The pathology is mostly papillary carcinoma. (2) The mass has clear borders, neatly shaped and hypoechoic inside, 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) The mass has a clear boundary with envelope, and the internal echogenicity is homogeneous or heterogeneous (may be accompanied by arcuate or plaque-like strong echogenic coarse calcification) or mixed with liquid and solid echogenicity. That is, “adenoma type”. (4) The mass has clear or indistinct borders and a liquid or mixed dark area inside. That is, “cystic change”. However, it is important to point out that: liquid dark areas or liquid-solid mixed echogenicity are not always caused by benign lesions; clear borders, envelope, and uniform internal echogenicity are not always manifested by 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.