title: The atypia of undetermined significance/follicular lesion of undetermined significance:malignant ratio: a proposed performance measure for reporting in The Bethesda System for thyroid cytopathology.
abstract: BACKGROUND
  The Bethesda System (TBS) for reporting thyroid cytopathology introduced the atypia of undetermined significance/follicular lesion of undetermined significance (AUS) category, but did not provide adequate guidance for the appropriate use of this diagnosis. In the current study, the authors sought to identify an appropriate measure for AUS use based on experience to date with TBS.
  
  
  METHODS
  The authors reviewed 8 series, including their own laboratory experiences, with a total of 30,466 thyroid aspirates classified within TBS.
  
  
  RESULTS
  The median AUS rate was 9.9% with a range of 3.0% to 18.0%. Use of the individual diagnostic categories within TBS varied up to 12.7-fold. The ratio of "suspicious for follicular neoplasm" plus "suspicious for malignancy" to "malignant" (M) diagnoses varied the least (1.8-fold). The AUS:M ratio provided a suitable measure of assessing AUS use, with a median ratio of 2.0 and a range of 0.5 to 4.9.
  
  
  CONCLUSIONS
  Based on available studies, an AUS:M ratio of 1.0 to 3.0 is recommended. AUS:M ratios > 3.0 are likely because of overdiagnosis of AUS or underdiagnosis of M. AUS:M ratios < 1.0 are mostly due to low AUS rates, at the likely expense of sensitivity.
authors.affiliation: Department of Pathology, Brigham and Women's Hospital, Boston, MA 02115, USA. jkrane@partners.org
authors.forename: Jeffrey F
authors.initials: JF
authors.lastname: Krane
authors.forename: Paul A
authors.initials: PA
authors.lastname: Vanderlaan
authors.forename: William C
authors.initials: WC
authors.lastname: Faquin
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Renshaw
mesh_terms: D018263:Adenocarcinoma, Follicular / Q000175:diagnosis* / Q000601:surgery; D044963:Biopsy, Fine-Needle; D006801:Humans; D013961:Thyroid Gland / Q000473:pathology* / Q000601:surgery; D013964:Thyroid Neoplasms / Q000175:diagnosis* / Q000601:surgery