title: The impact of atypia/follicular lesion of undetermined significance and repeat fine-needle aspiration: 5 years before and after implementation of the Bethesda System.
abstract: BACKGROUND
  Limited studies have examined the impact of the Bethesda System for Reporting Thyroid Cytopathology (BSRTC) and specifically the category of atypia or follicular lesion of undetermined significance (AUS/FLUS). We studied their effects on reporting rates, subsequent management, and surgical outcome over a 10-year period, 5 years before and after implementation of the BSRTC.
  
  
  METHODS
  A retrospective review of thyroid fine-needle aspiration (FNA) reports from 2003 to 2012 was performed. Diagnoses made before BSRTC were reclassified into the most appropriate category. Repeat FNA results for all AUS/FLUS cases were recorded. Surgical follow-up results were matched by side and size of the targeted nodule. Incidental microcarcinomas were not considered "malignant" on excision. Malignancy rates were calculated based on excision and by all aspirated specimens.
  
  
  RESULTS
  Initial AUS/FLUS cases increased from 3% to 7% (P = .001) with implementation of the BSRTC. The nondiagnostic rate decreased from 19% to 10% (P = .026). Differences in malignancy rates before and after implementation of the BSRTC were not significant for all diagnostic categories. More repeat FNAs and fewer surgical excisions were performed after an initial AUS/FLUS diagnosis. Repeat FNA reclassified 56% of AUS/FLUS cases into a definitive category. The malignancy risks for AUS/FLUS plus benign and AUS/FLUS plus AUS/FLUS repeat FNAs were elevated compared with single benign and AUS/FLUS diagnoses.
  
  
  CONCLUSIONS
  AUS/FLUS cases are increasing with the implementation of the BSRTC. Given the potential increase in repeat FNAs as a result, it may be important to alert the clinician regarding the elevated malignancy risk of a benign or AUS/FLUS diagnosis associated with a prior AUS/FLUS finding.
authors: Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, California.
authors: Peggy S
authors: PS
authors: Sullivan
authors: Sharon L
authors: SL
authors: Hirschowitz
authors: Po Chu
authors: PC
authors: Fung
authors: Sophia K
authors: SK
authors: Apple
mesh_terms: D018263:Adenocarcinoma, Follicular / Q000145:classification / Q000473:pathology*; D044963:Biopsy, Fine-Needle; D003581:Cytodiagnosis; D005500:Follow-Up Studies; D006284:Health Plan Implementation; D006801:Humans; D009367:Neoplasm Staging; D017410:Practice Guidelines as Topic; D011379:Prognosis; D012189:Retrospective Studies; D013961:Thyroid Gland / Q000473:pathology*; D013964:Thyroid Neoplasms / Q000145:classification / Q000473:pathology*
keywords: Bethesda System for Reporting Thyroid Cytopathology (BSRTC); atypia or follicular lesion of undetermined significance (AUS/FLUS); fine-needle aspiration; thyroid cytopathology