Thyroid nodules are lumps formed by localized growth of thyroid tissue or cysts containing fluid. Patients are most concerned about whether their nodules are benign or malignant, so thyroid doctors need to have a good eye to make basic judgments and give practical advice. What does an ultrasound image look like? 1, date nucleus The ultrasound characteristics of suspicious malignant thyroid nodules mention nodule aspect ratio (A/T) ≥ 1, in some cases the measurement of the upper and lower / anterior and posterior diameter ratio (L/A) < 1, which is also of reference significance and looks like a standing date nucleus on the ultrasound image, which is typical. It is said that malignant thyroid tumors grow in a "spherical" or "standing" position in order to bring more tumor cells into contact with surrounding tissues to obtain more nutrients and promote the growth of tumor cells, which is more sensitive in papillary carcinoma. This feature is more sensitive in papillary carcinoma, and papillary carcinoma accounts for a high proportion (80%) of thyroid carcinoma, so this ultrasound feature is of certain significance. The internal cystic structure of the nodule is divided into three categories: cystic, mixed cystic and solid. Adenomas can be classified as hyperechoic, isoechoic and hypoechoic according to the echogenicity of the parenchyma. Using papillary carcinoma as an example, most of them are solid nodules. As the liquefied portion increases, the possibility of nodule malignancy is decreasing, and the chance of cancer in completely cystic nodules is 0%. Because of the subjective factor in judging the ratio of cystic to solid structures, the reliability of judging the malignancy of nodules according to the cystic-to-solid ratio is low. In recent years, the proportion of papillary carcinoma showing mixed cystic-solid nature has increased. 3.Comet tail and microcalcifications Calcification is an ultrasound feature that requires vigilance. Nodules with calcification are twice as likely to be malignant as non-calcified nodules. And once calcification is present in a solitary, solid, hypoechoic node, the likelihood of its diagnosis as a malignant nodule approaches 80%. Papillary carcinomas can then present with various types of calcifications, with microcalcifications being the most common. Due to many factors such as the limitation of instrument resolution and the cognitive and judgmental ability of diagnosing physicians, many tiny strong echogenic foci inside nodes are misdiagnosed as microcalcifications. Minute strong echogenic foci are defined as strong echogenic foci less than 2 mm in diameter within a thyroid nodule without acoustic shadowing, and include forms such as colloid calcification or microcalcifications. Strong echogenic foci may be found in the following types of nodules: (1) follicular hyperplastic cysts, where the strong echogenic foci are mostly glial calcifications or glial crystals that are free from the liquefied area and are round or round-like with an inverted triangular posterior comet tail sign. (ii) Complex cystic nodules, mostly in two forms, one is flat and elongated adherent to fibrous compartment with or without comet tail sign posteriorly; the other is scattered in necrotic debris or parenchymal part, round, mostly with comet tail sign. (③ For malignant tumors mainly papillary carcinoma, microcalcifications as an indicator for the diagnosis of malignancy have the highest specificity (85.8%-95%) and positive prediction rate (41.8%-94.2%). Generally speaking, the comet's tail sign arises due to glial coagulation, which is mostly present in benign nodules, so it is mostly considered as a benign sign. However, the diagnosis of papillary carcinoma is largely established when the following conditions are met: round or spherical distribution, concentric lamellar calcium deposits, and location in the interstitial or lymphatic spaces of the tumor. Not all papillary carcinomas have gravelly bodies, but they are present in 40%-50% of papillary carcinomas. The ultrasound sensitivity of microcalcifications for the diagnosis of papillary carcinoma is not high, while the specificity is high. If the volume of microcalcifications is smaller and the number is more, the diagnostic reliability is higher. Papillary carcinoma may also present with coarse calcifications. The diagnostic value of coarse calcifications is lower than that of microcalcifications, but their occurrence is not low, and in many cases they are combined with microcalcifications. Previous studies have often attributed circumferential calcifications to dystrophy and are most often seen in benign nodules. Existing studies have found that 18.5% of nodules with peripheral calcification are malignant and 81.5% are benign, thus showing that follow-up of nodules should not be relaxed just because they present with peripheral calcification. In addition, Korean scholars found that interrupted peripheral calcification was more often seen in malignant nodules with an OR of 7.9. The presence of such ultrasound signs may be due to infiltrative growth of tumor cells that break through to the periphery. 4. Flamer The pattern of blood flow distribution in thyroid nodules is generally divided into four categories: Class I, no blood flow distribution; Class II, peripheral blood flow with no or very little internal blood flow distribution; Class III, both peripheral and internal blood flow distribution; Class IV, only internal blood flow with no peripheral blood flow distribution. The distribution of blood flow in thyroid nodules has also been classified into four classes: class I, nodules with no blood flow; class II, nodules with peripheral blood flow only; class III, moderate amount of blood flow passing from the periphery into the nodules; and class IV, nodules with abundant blood flow. Studies have concluded that color Doppler has a high value in the diagnosis of benign and malignant thyroid nodules, and that grade III and IV flow distribution patterns are characteristic of malignancy. Many studies have evaluated the predictive value of blood flow distribution patterns, with varying conclusions. The diagnostic value of using blood flow distribution pattern alone as a differential diagnosis criterion for benign and malignant is not high. Fine needle aspiration and biochemical examination Fine needle aspiration cytology of thyroid (fine needle aspiration FNA) is a very important test for the diagnosis of benign and malignant thyroid nodules. Based on the content of the ultrasound report, FNA is recommended if the nodule is inferred to have a risk of malignancy, which is important for the definitive diagnosis of thyroid cancer. It has the advantages of being invasive, painless, easy and convenient to operate, and has a high accuracy rate.