Generally speaking, whether benign or malignant, thyroid nodules show blood flow signals. For benign nodules, blood flow signals can be seen around the perimeter, with internal blood flow no different from normal thyroid tissue. In such cases, the nodules are typically diagnosed as thyroid adenomas, and they usually appear round or oval in shape with a uniformly echoic internal substance. If liquefaction occurs, mixed or cystic changes can appear; the tumor’s capsule tends to be intact, with clear boundaries. If a nodule has abundant internal blood flow with disorganized vessel distribution and high flow velocity, showing a high-resistance flow pattern, and has relatively less peripheral blood flow, it generally needs to be assessed for thyroid cancer. These nodules are often hypoechoic with irregular shapes, and the ratio of their longitudinal to transverse diameter is greater than 1. They have unclear boundaries, lack a capsule, and have no halo. In typical cases, microcalcifications like sand grains can also be observed. From the above analysis, we can see that the blood flow signals in thyroid nodules are complicated and reflect the extent of the nodular pathology. These signals can help in differentiating benign from malignant nodules, but when a rich and disorganized blood flow is observed, the nodule is more likely to be malignant.