title: Impact of reclassifying noninvasive follicular variant of papillary thyroid carcinoma on the risk of malignancy in The Bethesda System for Reporting Thyroid Cytopathology.
abstract: BACKGROUND
  Recent discussions have focused on redefining noninvasive follicular variant of papillary thyroid carcinoma (NI-FVPTC) as a neoplasm rather than a carcinoma. This study assesses the potential impact of such a reclassification on the implied risk of malignancy (ROM) for the diagnostic categories of The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC).
  
  
  METHODS
  The study consisted of consecutive fine-needle aspiration biopsy (FNAB) cases collected between January 1, 2013 and June 30, 2014 from 5 academic institutions. Demographic information, cytology diagnoses, and surgical pathology follow-up were recorded. The ROM was calculated with and without NI-FVPTC and was presented as a range: all cases (ie, overall risk of malignancy [OROM]) versus those with surgical follow-up only.
  
  
  RESULTS
  The FNAB cohort consisted of 6943 thyroid nodules representing 5179 women and 1409 men with an average age of 54 years (range, 9-94 years). The combined average ROM and OROM for the diagnostic categories of TBSRTC were as follows: nondiagnostic, 4.4% to 25.3%; benign, 0.9% to 9.3%; atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS), 12.1% to 31.2%; follicular neoplasm (FN), 21.8% to 33.2%; suspicious for malignancy (SM), 62.1% to 82.6%; and malignant, 75.9% to 99.1%. The impact of reclassifying NI-FVPTC on the ROM and OROM was most pronounced and statistically significant in the 3 indeterminate categories: the AUS/FLUS category had a decrease of 5.2% to 13.6%, the FN category had a decrease of 9.9% to 15.1%, and the SM category had a decrease of 17.6% to 23.4% (P < .05), whereas the benign and malignant categories had decreases of 0.3% to 3.5% and 2.5% to 3.3%, respectfully. The trend of the effect on the ROM and OROM was similar for all 5 institutions.
  
  
  CONCLUSIONS
  The results from this multi-institutional cohort indicate that the reclassification of NI-FVPTC will have a significant impact on the ROM for the 3 indeterminate categories of TBSRTC.
authors.affiliation: Massachusetts General Hospital, Boston, Massachusetts.
authors.forename: William C
authors.initials: WC
authors.lastname: Faquin
authors.affiliation: Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Lawrence Q
authors.initials: LQ
authors.lastname: Wong
authors.affiliation: Massachusetts General Hospital, Boston, Massachusetts.
authors.forename: Amir H
authors.initials: AH
authors.lastname: Afrogheh
authors.affiliation: Johns Hopkins Hospital, Baltimore, Maryland.
authors.forename: Syed Z
authors.initials: SZ
authors.lastname: Ali
authors.affiliation: Johns Hopkins Hospital, Baltimore, Maryland.
authors.forename: Justin A
authors.initials: JA
authors.lastname: Bishop
authors.affiliation: Institute of Pathology, University Hospital, Lausanne, Switzerland.
authors.forename: Massimo
authors.initials: M
authors.lastname: Bongiovanni
authors.affiliation: Geneva University Hospitals, Geneva, Switzerland.
authors.forename: Marc P
authors.initials: MP
authors.lastname: Pusztaszeri
authors.affiliation: Johns Hopkins Hospital, Baltimore, Maryland.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: VandenBussche
authors.affiliation: Institute of Pathology, University Hospital, Lausanne, Switzerland.
authors.forename: Jolanta
authors.initials: J
authors.lastname: Gourmaud
authors.affiliation: Massachusetts General Hospital, Boston, Massachusetts.
authors.forename: Louis J
authors.initials: LJ
authors.lastname: Vaickus
authors.affiliation: Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Zubair W
authors.initials: ZW
authors.lastname: Baloch
mesh_terms: D018263:Adenocarcinoma, Follicular / Q000473:pathology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D044963:Biopsy, Fine-Needle; D002277:Carcinoma / Q000145:classification / Q000473:pathology* / Q000601:surgery; D002291:Carcinoma, Papillary; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012306:Risk; D000077273:Thyroid Cancer, Papillary; D013964:Thyroid Neoplasms / Q000145:classification / Q000473:pathology* / Q000601:surgery
keywords: Bethesda; atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS); fine-needle aspiration (FNA); follicular variant; noninvasive; noninvasive follicular thyroid (NIFT); papillary thyroid carcinoma; thyroid