Abstract: Background　Since the ultrasonographic findings of both focal subacute granulomatous thyroiditis（FSGT） and papillary thyroid carcinoma（PTC） have much in common，which implies that clinical misdiagnosis could happen and that may result in unnecessary surgeries upon patients.Objective　This study is aimed at enhancing the sonographers' differential diagnosis ability in recognizing FSGT through differentially analyzing the ultrasonographic appearance between FSGT and PTC.Methods　A retrospective study was conducted.Participants were recruited from First Hospital of Shanxi Medical University，including 18 with postoperatively pathology-confirmed FSGT（23 thyroid nodules in total） treated between January 2013 and July 2019，and 63 with PTC confirmed by repeated postoperative pathology tests （70 thyroid nodules in total） treated from February 2017 to October 2019.Characteristics of routine ultrasonography were collected，including echoes，internal structure of nodules，homogeneity of echo intensity，nodule margin，Adler grade of blood flow in thyroid nodules，anteroposterior-transverse ratio，and punctate hyperechogenic foci.Besides，intraoperative nodule conditions were also collected，including adhesion or invasion of the nodule capsule，nodule texture，and the relationship between the nodule and peripheral thyroid glands.Results　There were no significant differences in echoes，homogeneity of echo intensity，Adler grade of blood flow between FSGT and PTC nodules（P>0.05）.The prevalence of anteroposterior-transverse ratio ≤1 was higher and that of punctate hyperechogenic foci was lower in FSGT nodules（P<0.05）.There were no significant differences in adhesion or invasion of the nodule capsule，and the nodule texture（P>0.05），FSGT nodules had higher prevalence of having a more evident boundary with surrounding thyroid glands（P=0.003）.Conclusion　Although FSGT and PTC possess similar ultrasonographic characteristics，but FSGT nodules may have higher prevalence of anteroposterior-transverse ratio ≤1 and lower prevalence of punctate hyperechogenic foci.Therefore，a comprehensive analysis should be implemented during clinical work to exclude the possibility of painless FSGT，and fine needle aspiration is indispensable to prevent patients from misdiagnosis and unnecessary surgeries.

Key words: Subacute granulomatous thyroiditis, Thyroid neoplasms, Ultrasonography, Elasticity imaging techniques, Diagnostic errors

摘要： 背景　局灶性亚急性肉芽肿性甲状腺炎（FSGT）和甲状腺乳头状癌（PTC）的超声表现有相似之处，临床中存在误诊而行不必要的手术。目的　分析FSGT与PTC的超声图像特征，旨在提高超声医师对FSGT的鉴别能力。方法　回顾性分析2013年1月—2019年7月在山西医科大学第一医院就诊并术后经病理确诊的FSGT患者，共18例23个结节；连续性选取2017年2月—2019年10月在本院经手术病理确诊的PTC患者，共63例70个结节。记录两组常规超声特征，包括回声、结节内部结构、回声均匀性、边缘、血流信号分级、纵横比、点状强回声情况。记录术中结节粘连或侵犯包膜、结节质地情况、结节与周围甲状腺腺体的关系。结果　FSGT和PTC患者结节回声、回声均匀性、血流信号分级比较，差异均无统计学意义（P>0.05）；FSGT患者结节纵横比≤1所占比例高于PTC患者，点状强回声所占比例低于PTC患者（P<0.05）。FSGT与PTC患者结节粘连或侵犯包膜所占比例、术中质地比较，差异无统计学意义（P>0.05）；FSGT患者结节与周围甲状腺体边界清所占比例高于PTC患者（P=0.003）。结论　FSGT与PTC虽在超声图像上相似，但FSGT较PTC纵横比≤1更多见、点状强回声出现少，在临床工作中应综合分析以除外无痛性FSGT的可能，细针穿刺活检非常必要，以避免误诊而引起不必要的手术。

关键词: 亚急性肉芽肿性甲状腺炎, 甲状腺癌, 超声检查, 弹性成像技术, 误诊