Hashimoto Thyroiditis: Part 1, Sonographic Analysis of the Nodular Form of Hashimoto Thyroiditis

OBJECTIVE. The purpose of this article is to analyze the sonographic appearance of nodular Hashimoto thyroiditis. SUBJECTS AND METHODS. As part of an ongoing multiinstitutional study, patients who underwent ultrasound examination and fine-needle aspiration of one or more thyroid nodules were analyzed for multiple predetermined sonographic features. Patients completed a questionnaire, including information about thyroid function and thyroid medication. Patients (n = 61) with fine-needle aspiration cytologic results consistent with nodular Hashimoto thyroiditis (n = 64) were included in the study. RESULTS. The mean (+/- SD) diameter of nodular Hashimoto thyroiditis was 15 +/- 7.33 mm. Nodular Hashimoto thyroiditis occurred as a solitary nodule in 36% (23/64) of cases and in the setting of five or more nodules in 23% (15/64) of cases. Fifty-five percent (35/64) of the cases of nodular Hashimoto thyroiditis occurred within a sonographic background of diffuse Hashimoto thyroiditis, and 45% (29/64) of cases occurred within normal thyroid parenchyma. The sonographic appearance was extremely variable. It was most commonly solid (69% [42/61] of cases) and hypoechoic (47%[27/58] of cases). Twenty percent (13/64) of nodules had calcifications (seven with nonspecific bright reflectors, four with macrocalcifications, and three eggshell), and 5% (3/64) of nodules had colloid. Twenty-seven percent (17/64) of nodules had a hypoechoic halo. The margins were well defined in 60% (36/60) and ill defined in 40% (24/60) of nodules. On Doppler analysis, 35% (22/62) of nodules were hypervascular, 42% (26/62) were isovascular or hypovascular, and 23% (14/62) were avascular. CONCLUSION. The sonographic features and vascularity of nodular Hashimoto thyroiditis were extremely variable.