Abstract] Objective To explore the significance of preoperative ultrasound in the diagnosis of thyroid cancer and the evaluation of cervical lymph node metastasis. Methods We retrospectively analyzed the clinical data of 129 patients with thyroid cancer who underwent surgical treatment in our hospital in 2009. The preoperative color ultrasound examination of this group of patients revealed solid or cystic nodules in the thyroid gland, of which 88 cases (82%) were hypoechoic, 87 cases (73%) were associated with calcified foci, 41 cases (60%) were with unclear borders, and 43 cases (47%) were with abundant blood flow. The specificity of color ultrasound for the evaluation of cervical lymph node metastasis was 88%, and the sensitivity was 38%. Conclusion: Ultrasound parameters such as hypoechoic nodules, calcified foci, unclear nodule boundaries, and abundant blood flow are important bases for preoperative diagnosis of thyroid cancer, and preoperative ultrasound has a high specificity for the diagnosis of cervical lymph node metastasis, which can also be used as one of the indications for whether or not to perform cervical lymph node dissection. Keywords] Thyroid cancer, color ultrasound, classification number] R653 [Identification number Thyroid cancer is a common disease, and its incidence is increasing year by year [1]. Because of its insidious clinical manifestations, lack of specific symptoms, and often combined with nodular goiter, chronic lymphocytic thyroiditis, hyperthyroidism and other benign diseases, it is easy to be overlooked by patients and doctors and missed and misdiagnosed. In recent years, with the continuous progress of ultrasound imaging technology, its preoperative detection rate has been greatly improved. Now we summarize and report the characteristics of ultrasonic imaging of thyroid cancer patients admitted in our hospital last year as follows. Clinical data General data There were 129 patients in this group, 97 female and 32 male, the ratio of both was 3:1. age 12~78 years old, average 43 years old. All patients were examined by color ultrasound before surgery, which indicated solid or cystic nodules in the thyroid gland: the size of the nodules was 0.2-6.1 cm, with an average of 1.8 cm; among them, there were 46 cases of solitary nodules and 73 cases of multiple nodules; 88 cases of hypoechoic nodules accounted for 82% (88/129); 87 cases of nodules were accompanied by calcified foci, which accounted for 73% (87/129); and 41 cases of nodules with unclear boundaries accounted for 60% (41/129); and 41 cases with unclear boundaries accounted for 60% (41/129); the mean age was 12-78 years old. There were 41 cases with unclear nodule boundaries, accounting for 60% (41/129); 43 cases with rich nodule blood flow, accounting for 47% (43/129). Postoperative pathology confirmed thyroid cancer, including 118 cases of differentiated thyroid cancer, 3 cases of medullary carcinoma and 8 cases of undifferentiated carcinoma. About 30% (40/129) of the patients had concomitant benign diseases such as nodular goiter, chronic lymphocytic thyroiditis and hyperthyroidism. Surgical treatment All patients in this group underwent surgical treatment, including 116 cases of radical surgery, 9 cases of local or lateral lobectomy, and 4 cases of palliative resection due to extensive infiltration of the tumor. Lymph node dissection was performed in 113 cases, including 10 cases of functional cervical dissection and 103 cases of selective cervical lymph node dissection. Preoperative color ultrasound suggested lymph node metastasis in 28 cases, of which 21 cases were confirmed as metastasis by postoperative pathology; the specificity of color ultrasound for the diagnosis of preoperative lymph node metastasis was 88%, and the sensitivity was 38% (see Table I). Results No serious complications occurred during the perioperative period in this group of patients. Discussion Ultrasound characteristics of thyroid cancer Thyroid cancer lacks specific symptoms, and its clinical manifestations are not easy to distinguish from benign diseases such as nodular goiter and thyroid adenoma, so the rate of correct preoperative diagnosis is not high. Although fine-needle aspiration examination can obviously improve the preoperative detection rate [2], it is difficult for some patients to accept because it is an invasive examination, and its positive rate is closely related to the experience and technical level of the ultrasound and pathologists, so its application has been greatly restricted and is difficult to be widely used in the clinic. Color ultrasound has many advantages, such as economic, non-invasive, reproducibility, etc., and has become the first choice of thyroid cancer examination. In recent years, with the progress of this technology, the diagnostic rate of thyroid cancer has been improved to a great extent, and the domestic literature reports [3] that the compliance rate of preoperative color ultrasound for thyroid cancer diagnosis can be as high as 88%. Ultrasound features such as hypoechoic nodules, irregular morphology, unclear borders, and calcification are all suggestive of malignant risk factors. Whether the nodule is solitary or not, the size of the nodule, gender and other factors have no significant correlation with malignancy. In addition, the above ultrasound features alone are not ideal for determining the benign or malignant nature of the nodule, but if they are applied in combination, their diagnostic sensitivity can be greatly improved [4]. Therefore, the possibility of thyroid cancer should be alerted to the presence of thyroid nodules with two or more of the above features on ultrasound. Ultrasound evaluation of lymph node metastasis in thyroid cancer Although the prognosis of thyroid cancer is better than that of malignant tumors in other parts of the body, inappropriate treatment often causes greater physical and psychological pain to patients. The surgical approach has an important impact on the prognosis of patients with thyroid cancer [5]. Currently, there is some disagreement on whether to perform prophylactic lymph node dissection for thyroid cancer. However, for those with clear preoperative lymph node metastasis, the opinions are still more unified. There are many methods for determining cervical lymph node metastasis in thyroid cancer [6], but none of them are highly accurate. Our experience is to judge whether there is lymph node metastasis based on preoperative color ultrasound examination and intraoperative exploration for the presence of cervical lymph node enlargement. The indicators of lymph node metastasis judged by color ultrasound are: lymph node enlargement, loss of normal morphology, unclear demarcation of corticomedullary stroma, and internal accompanied by tiny calcification or liquefaction. For positive patients, we routinely performed cervical lymph node dissection. In our group, there were 28 cases of cervical lymph node enlargement detected by preoperative color ultrasound, of which 21 cases were confirmed as lymph node metastatic cancer by postoperative pathology. The specificity of color ultrasound for the diagnosis of cervical lymph node metastasis was as high as 88%, which was similar to that reported in domestic and foreign literature. Therefore, we believe that preoperative color ultrasound examination is of guiding significance in determining cervical lymph node metastasis and can be used as one of the indications for cervical lymph node dissection. However, since the sensitivity of color ultrasound in determining cervical lymph node metastasis is relatively low, which was only 38% in our group, the decision of whether to perform lymph node dissection in patients with negative cervical lymph nodes indicated by color ultrasound should be made according to the intraoperative situation. In summary, color ultrasound should be routinely performed in patients with thyroid nodules. Ultrasound features such as hypoechoic nodules, irregular morphology, unclear borders, and calcification should be actively treated with surgery. If preoperative ultrasound suggests that cervical lymph nodes are enlarged or intraoperative exploration reveals that cervical lymph nodes are enlarged, cervical lymph node dissection should be performed.