OBJECTIVETo compare the ultrasound imaging characteristics of benign and malignant thyroid nodules on the background of Hashimoto's thyroiditis (HT).

METHODSTotally 120 consecutive patients with pathologically confirmed benign (n=60) or malignant (n=60) thyroid nodules in Peking Union Medical College Hospital since January 2013 were retrospectively analyzed, and their preoperative ultrasound images were reviewed.

RESULTSSixty cases (100%) of the malignant nodules were papillary thyroid cancers. In the benign group, 33 cases (55.0%) had nodular changes of HT, 26 (43.3%) had nodular goiter, and one (16.7%) had adenoma. Compared with the benign ones,the malignant nodules were more likely to be solid (91.7% vs. 68.3%, P=0.001), hypoechoic (96.7% vs. 48.3%, P=0.000), ill defined (95.0% vs. 41.7%, P=0.000), irregular (96.7% vs. 43.4%, P=0.000), and more easily to have such characteristics as micro-calcification (71.7% vs. 30.0%, P=0.000), absence of regular halo (96.7% vs. 65.0%, P=0.000), taller-than-wide sign (46.7% vs. 13.3%, P=0.000), and locally increased or irregular blood flow (61.7% vs. 26.7%, P=0.000).

CONCLUSIONSUltrasound has an ideal overall sensitivity in differentiating nodules on the background of HT. Solid structure, hypo-echogenicity, ill-defined margin, irregular shape, and absence of regular halo are good screening ultrasound markers. Except for the A/T≥1, the other variables have less satisfactory diagnostic specificity.