title: Spectrum of risk of malignancy in subcategories of 'atypia of undetermined significance'.
abstract: OBJECTIVE
  To determine if focal 'nuclear atypia' or 'microfollicular architecture' portends a higher risk of malignancy than other subcategories of atypia of undetermined significance (AUS) in thyroid fine-needle aspirations (FNAs).
  
  
  METHODS
  The frequencies of The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) categories were calculated from 3,956 thyroid FNAs interpreted over a 26-month period at The Johns Hopkins Hospital after adoption of TBSRTC. TBSRTC criteria were applied strictly. The risk of malignancy, specifically for AUS subcategories, was analyzed by cyto-histo correlation.
  
  
  RESULTS
  Of the 133 cases diagnosed as AUS, 32% were found to have stageable carcinoma (not incidental microcarcinoma) on resection. When the subset of AUS with 'nuclear atypia' (AUS-N) was separated from other AUS cases, 48% (30/62) of them had stageable carcinoma on resection; of the AUS subset with 'microfollicular architecture' (AUS-F), 27% (8/30) were malignant on resection. The 'suspicious for papillary thyroid carcinoma' (SPTC) group maintained a higher risk of malignancy versus AUS-N (relative risk, RR 1.57; 95% CI 1.23-1.81).
  
  
  CONCLUSIONS
  The subcategory of 'nuclear atypia' within AUS indicates a higher risk of malignancy than other subcategories of AUS but has a lower risk of malignancy than SPTC does. Thus, it is an important distinction with potential clinical implications.
authors.affiliation: Department of Pathology, The Johns Hopkins Hospital, Baltimore, Md., USA.
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Olson
authors.forename: Douglas P
authors.initials: DP
authors.lastname: Clark
authors.forename: Yener S
authors.initials: YS
authors.lastname: Erozan
authors.forename: Syed Z
authors.initials: SZ
authors.lastname: Ali
mesh_terms: D000328:Adult; D000368:Aged; D044963:Biopsy, Fine-Needle; D002277:Carcinoma / Q000145:classification / Q000175:diagnosis* / Q000473:pathology*; D002471:Cell Transformation, Neoplastic / Q000473:pathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D017410:Practice Guidelines as Topic; D011379:Prognosis; D012189:Retrospective Studies; D012306:Risk; D009626:Terminology as Topic; D013961:Thyroid Gland / Q000473:pathology*; D016606:Thyroid Nodule / Q000145:classification / Q000175:diagnosis* / Q000473:pathology*