Managing TBSRTC III thyroid nodules: evaluating repeat FNA, molecular testing, and surgery

Thyroid nodules are common, but most are benign. Concerning nodules undergo fine-needle aspiration (FNA) and are classified using The Bethesda System. Nodules with atypia of undetermined significance (AUS) [Bethesda III] have management options including surveillance, repeat FNA, molecular testing, and surgical evaluation. While molecular testing can reduce unnecessary surgeries, it is costly. This retrospective study assessed the feasibility of repeat FNA as a cost-effective alternative.

We conducted a multi-institutional retrospective study of AUS nodules from 5 hospitals between September 1, 2018, and March 1, 2024. Only initial FNA cases were included; pediatric cases and those lost to follow up were excluded. Nodules were stratified by initial diagnostic choice (repeat FNA, molecular testing, surgical intervention). Clinical and ultrasonography findings were reviewed to determine associations with malignancy rates. Costs were estimated based on Medicare reimbursement rates.

We identified 2649 nodules that underwent FNA, with 199 interpreted as AUS. Of these, 131 met the criteria. Repeat FNA resulted in a benign diagnosis in 48.7% of cases and AUS in 35.9%. Costs were lowest for nodules undergoing repeat FNA. There was no significant difference in rates of surgical intervention or malignancy compared to molecular testing. American College of Radiology Thyroid Imaging Reporting and Data System categories were not associated with malignancy rates. Only echogenic foci were significantly associated with malignancy (P = 0.03).

Repeat FNA resolved approximately 50% of cases, with no significant differences in malignancy or surgical intervention rates compared to molecular testing. Repeat FNA is the most cost-effective initial step for managing AUS nodules. Prebiopsy ultrasonography had limited utility in stratifying malignancy risk for AUS nodules.