Malignancy risk and characteristics of thyroid nodules with two consecutive results of atypia of undetermined significance or follicular lesion of undetermined significance on cytology.

Abstract

To evaluate the malignancy risk and characteristics of thyroid nodules with two "Atypia of Undetermined Significance" or "Follicular Lesion of Undetermined Significance" (AUS/FLUS) results, and compare characteristics of malignancies with two AUS/FLUS results to those with one AUS/FLUS result. Of 441 thyroid nodules with initial AUS/FLUS results, 236 underwent repeat fine-needle-aspiration (FNA), with 58 obtaining repeated AUS/FLUS results. Thyroid Imaging Reporting and Data System (TIRADS) categories were assigned, and clinico-pathological characteristics were compared between benign and malignant nodules and between malignancies with two consecutive AUS/FLUS results and those with one AUS/FLUS result. Thirty-one percent (18/58) of nodules with two AUS/FLUS results and 58.1% (18/31) of confirmed nodules were malignant. Age, gender, nodule size, ultrasound features and TIRADS categories did not differ between benign and malignant nodules or between malignancies with one and two AUS/FLUS results. Malignancies with two AUS/FLUS results had a higher proportion of a follicular variant of papillary thyroid carcinoma (PTC) (46.7% vs. 13.6%, P = 0.009). Thyroid nodules with two AUS/FLUS results had a high malignancy risk of at least 31.0% and a higher proportion of a follicular variant of PTC. Surgery should be considered regardless of ultrasound features. • Thyroid nodules with two consecutive AUS/FLUS results had a high malignancy risk. • Ultrasound features are less useful in nodules with two AUS/FLUS results. • The follicular variant of PTC is more frequent in malignancies with two AUS/FLUS results.