Fine-needle aspiration of follicular patterned lesions of the thyroid: diagnosis, management, and follow-up according to thyroid Bethesda system.

Objective: The goal of this study was to report an experience with thyroid fine-needle aspiration (FNA) cases that can be placed into National Cancer Institute-designated thyroid FNA diagnostic categories for follicular patterned lesions divided into three diagnostic categories: follicular lesion of undetermined significance/atypia of undetermined significance (AUS/FLUS), suspicious for follicular neoplasm (SFON), and suspicious for malignancy.

Study Design: The study cohort included 4,284 cases for the period between January 2007 and July 2011 and all available follow-up data was obtained. All cases classified as 'atypical' and 'rule out follicular neoplasm' were included in the AUS/FLUS category (n = 3,903), whereas cases classified as 'suspicious for' or 'consistent with follicular or Hürthle cell neoplasm' (n = 381) were included in the SFON diagnostic category and compared with histopathologic follow-up.