Management of Thyroid Nodules with Atypical Cytology on Fine-needle Aspiration Biopsy

Abstract

Fine-needle aspiration biopsy (FNAB) of the thyroid categorized as atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) is a newly defined category according to the recent Bethesda guidelines. We sought to assess the characteristics and treatment of patients with an AUS/FLUS FNAB at our institution. Additionally, we evaluated the utility of the recommended 3-month timing of repeat FNAB. A retrospective study of all patients with an FNAB categorized as AUS/FLUS at an academic tertiary-care center. Clinical, cytological, and ultrasound variables were compared among management groups. Differences in patients receiving repeat FNAB before or after a 3-month interval were compared. A total of 203 patients of the 5,391 FNABs performed at our institution met the Bethesda criteria for AUS/FLUS; 62% were sent directly to surgery, 25% had a repeat FNAB, and 13% were observed. Younger (p=0.006) and male patients (p=0.04) were more likely to go directly to surgery. Microcalcifications, irregular margins, and marked hypoechogenicity on ultrasound did not appear to influence the decision to repeat the FNAB, observe the patient, or refer the patient for surgery. Timing of repeat FNAB (<3 months or ≥3 months) did not alter the diagnostic results of the second FNAB (p=0.73). The overall rate of malignancy in patients undergoing surgery was 15.7%. Gender and age, not ultrasound characteristics, appear to influence the decision for surgery in AUS/FLUS patients. Timing of repeat biopsy did not alter management, repeat FNAB diagnosis, or rate of malignancy in our cohort.