Malignancy rate associated with Bethesda category III (AUS/FLUS) with and without repeat fine needle aspiration biopsy.

Abstract

Selection of nodules for surgery diagnosed as Bethesda category III [atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) category] is important. It was aimed to define the malignancy rates associated with and without repeat fine needle aspiration biopsy (FNAB) and to define the contribution of repeat FNAB to triage to surgery or observation in nodules with AUS/FLUS FNAB. The records of all patients with nodules who underwent FNAB and classified by Bethesda reporting system as AUS/FLUS at their institution were reviewed. Malignancy rates for patients with AUS/FLUS FNAB with and without repeat FNAB were calculated. Of the 582 patients who were classified as AUS/FLUS on initial FNAB, 179 underwent surgery with an associated malignancy rate of 22.9% (upper boundary). Risk of malignancy among all patients with AUS/FLUS nodules was 7% (lower boundary). The upper and lower boundaries of the malignancy rates with and without repeat FNAB were 38.6% and 15.6% for resected patients, and 13% and 4.6% for all patients, respectively. Reclassification rate with repeat FNAB was 56%. The findings showed that repeat FNAB for initial AUS/FLUS category was associated with a significantly increased malignancy rate compared with those without repeat FNAB. Repeat FNAB could help selection of patients with AUS/FLUS to triage to surgery. Therefore, repeat FNAB for nodules with AUS/FLUS on initial FNAB was suggested.