[Abstract] Objective To investigate the ultrasound manifestations of nodular Hashimoto’s thyroiditis. Methods We retrospectively summarized and analyzed the ultrasound manifestations of 20 cases of nodular Hashimoto’s thyroiditis, and compared the ultrasound characteristics of nodular Hashimoto’s thyroiditis and papillary thyroid carcinoma underlying Hashimoto’s thyroiditis in terms of size of thyroid gland, number of lesions, echogenicity, blood flow signal, calcification, acoustic halo and enlarged lymph nodes in the neck, etc. We also compared the ultrasound characteristics of nodular Hashimoto’s thyroiditis with those of papillary thyroid carcinoma underlying Hashimoto’s thyroiditis. The results showed that nodular Hashimoto’s thyroiditis with enlarged glands and multiple lesions were more common, mostly showing moderate to high echogenicity with acoustic corona, calcification, very low echogenicity and cystic changes. The differences in gland size, number of lesions, echogenicity, acoustic halo and calcification were statistically significant in both groups compared with the papillary thyroid carcinoma group on the basis of Hashimoto’s thyroiditis (all P < 0.05). Conclusion There are differences in ultrasound manifestations between nodular Hashimoto's thyroiditis and papillary thyroid carcinoma on the basis of Hashimoto's thyroiditis, which can help to differentiate them. Hashimoto's thyroiditis (HT), also known as chronic lymphocytic thyroiditis, is an autoimmune disease that is more common in middle-aged and elderly women, and is characterized by a diffusely enlarged and tough thyroid gland, which often appears on ultrasound as a heterogeneous glandular echogenicity with a small nodular appearance ( Micronodulation) [1-4]. However, HT is not always a diffuse process and can sometimes present as a focal, palpable mass with a "pseudotumor" appearance, called nodular Hashimoto's thyroiditis (NHT) [5-8]. In this study, we aim to improve the ultrasound diagnosis of NHT by summarizing the ultrasound manifestations of NHT and comparing it with papillary thyroid carcinoma (PTC), the most common malignant tumor underlying HT. 1 Data and methods 1.1 General data Twenty patients with NHT confirmed by surgical pathology in our hospital from December 2006 to December 2008 were selected. All were female, aged 25-68 years, with a median age of 51 years. All patients were seen for thyroid nodules or thick neck or anterior neck swellings found on physical examination, and the duration of disease ranged from more than 10 days to more than 10 years. 1 patient (1/20,5.00%) had a sensation of holding pressure in the neck for nearly 1 year, 6 patients (6/13,46.2%) had normal thyroid function, and 7 patients (7/13,53.8%) had subclinical hypothyroidism; of the 12 patients who received thyroid antibody tests Among the 12 patients who underwent thyroid antibody examination, 10 cases (83.33%, 10/12) had elevated anti-thyroglobulin antibodies or anti-peroxidase antibodies, and 2 cases (16.67%, 2/12,) had normal thyroid antibody levels. 1.2 Apparatus and methods A GE logiq 9, Philips IU 22, and Philips HDI 5000 ultrasound diagnostic instruments were used for thyroid and cervical lymph node examinations, with probe frequencies of 5-12 MHz, all superficial line array probes, and gray-scale and color Doppler ultrasonography pre-conditioned for thyroid or superficial organ examination conditions. Ultrasonography: The patient is placed in a supine position, and the thyroid is scanned in multiple views in front of the neck to measure the size of the gland, observe the background echogenicity of the gland, the presence of nodules in the gland, the size of the nodules, the internal echogenicity of the nodules, the blood flow in the nodules and the gland, and the lymph nodes in the neck. Ultrasound analysis: gland thickness over 2.0 cm on either side was defined as gland enlargement; gland echogenicity was defined as homogeneous and heterogeneous; nodule echogenicity equal to or lower than the neck muscle was defined as very low echogenicity, between the neck muscle and the thyroid gland as low echogenicity, and equal to or higher than the gland as moderate to high echogenicity; nodule size was counted as the largest diameter; according to the richness of blood flow signal, blood flow was defined as "no blood". When the short axis of the lymph node was larger than 0.5 cm, the lymphatic portal hyperechoic structure disappeared, and the internal echogenicity was also absent. When the short axis of the lymph node was larger than 0.5 cm, the high echogenic structure of the lymphatic gate was lost, and any of the signs such as internal echogenic inhomogeneity, irregular blood flow signal, calcification or cystic change were also present, it was defined as abnormal enlargement of lymph nodes in the neck. The description of the lesion was confirmed to correspond to the surgical lesion during sonographic analysis. Another 40 patients with PTC on the basis of HT confirmed by surgical pathology in our hospital during the same period were selected as the control group to compare the differences in the main ultrasound features between the two groups. 1.3 Statistical treatment SPSS 11.5 statistical software was used. For the control study of NHT and HT-based PTC, nodule size was compared using the t-test, and other count data were compared using the c2 test, and P<0.05 was considered a statistically significant difference. All 20 cases of NHT were confirmed by surgical pathology and showed the presence of HT in the thyroid gland. 2.1 Ultrasound manifestations of NHT In terms of background ultrasound manifestations of the gland, 19 cases (95.00%) of patients with NHT had enlarged thyroid glands, 20 cases had glandular echogenicity, 4 cases (20.00%) had a single lesion in the thyroid gland, and 16 cases (80.00%) had 2 or In 16 cases (80.00%), there were two or more lesions. In 15 cases (75.00%), the lesions were moderately hyperechoic; 3 cases (15.00%) were hypoechoic; 2 cases (10.00%) were very hypoechoic (Figure 2); 12 cases (60.00%) had a hypoechoic halo around the lesion, and 1 case had a cystic component inside the moderately hyperechoic lesion. 2 cases (10.00%) had calcifications inside the lesion, including 1 case with moderate to high echogenicity. Coarse calcifications were seen inside the lesion (Figure 5), and microcalcifications were seen inside the echogenic lesion in one case. Among the 13 lesions described with blood flow signal, 5 (38.46%, 5/13) had abundant blood flow signal, 7 (53.85%, 7/13) had visible blood flow signal, and 1 (7.69%, 1/13) had no blood flow signal. 3 (15.00%) had abnormally enlarged cervical lymph nodes.