title: Impact of Reclassification on Thyroid Nodules with Architectural Atypia: From Non-Invasive Encapsulated Follicular Variant Papillary Thyroid Carcinomas to Non-Invasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features.
abstract: BACKGROUND
  The follicular variant of papillary thyroid cancer (FVPTC), especially the encapsulated non-invasive subtype, is a controversial entity. Recent study suggested using 'non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP)' for these indolent carcinomas. We evaluated the impact of reclassification from non-invasive encapsulated FVPTCs (EFVPTCs) to NIFTPs in the diagnosis of thyroid nodules with architectural atypia.
  
  
  METHODS
  We reviewed 1301 thyroid nodules with architectural atypia in core needle biopsy (CNB) specimens obtained from March 2012 to February 2013. Nodules were classified into atypia of undetermined significance with architectural atypia (AUS-A, 984, 76%) or follicular neoplasm/suspicious for a follicular neoplasm (FN/SFN, 317, 24%). Among them, diagnostic surgery was performed in 384 nodules (30%).
  
  
  RESULTS
  In total, 160 nodules (42%) presented final malignant diagnoses including 39 non-invasive encapsulated FVPTCs (10%). The malignancy rate was estimated to be 7-35% in AUS-A nodules and 28-49% in FN/SFN nodules. After reclassification, the malignancy rate was much decreased and estimated to be 5-24% in AUS-A nodules, and 23-39% in FN/SFN nodules. Thyroid nodules with final malignant diagnoses were significantly more likely to have a FN/SFN CNB diagnosis, malignant US features and concomitant nuclear atypia in CNB specimens. However, these factors could not differentiate NIFTPs from other malignancies.
  
  
  CONCLUSIONS
  After reclassification of non-invasive EFVPTCs to NIFTPs, the malignancy rate of thyroid nodules with architectural atypia in CNB specimens was decreased. However, there were no preoperative factors differentiating other malignancies from NIFTPs. The presence of malignant US features or concomitant nuclear atypia might help clinicians deciding diagnostic surgery but, these features also might indicate NIFTPs.
authors.affiliation: Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Min Ji
authors.initials: MJ
authors.lastname: Jeon
authors.affiliation: Department of Pathology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Dong Eun
authors.initials: DE
authors.lastname: Song
authors.affiliation: Department of Hospital Pathology, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Chan Kwon
authors.initials: CK
authors.lastname: Jung
authors.affiliation: Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Won Gu
authors.initials: WG
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Hyemi
authors.initials: H
authors.lastname: Kwon
authors.affiliation: Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Yu-Mi
authors.initials: YM
authors.lastname: Lee
authors.affiliation: Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Tae-Yon
authors.initials: TY
authors.lastname: Sung
authors.affiliation: Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Jong Ho
authors.initials: JH
authors.lastname: Yoon
authors.affiliation: Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Ki-Wook
authors.initials: KW
authors.lastname: Chung
authors.affiliation: Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Suck Joon
authors.initials: SJ
authors.lastname: Hong
authors.affiliation: Department of Radiology and Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Jung Hwan
authors.initials: JH
authors.lastname: Baek
authors.affiliation: Department of Radiology and Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Jeong Hyun
authors.initials: JH
authors.lastname: Lee
authors.affiliation: Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Tae Yong
authors.initials: TY
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Young Kee
authors.initials: YK
authors.lastname: Shong
authors.affiliation: Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Won Bae
authors.initials: WB
authors.lastname: Kim
mesh_terms: D018263:Adenocarcinoma, Follicular / Q000175:diagnosis* / Q000473:pathology; D000328:Adult; D002277:Carcinoma / Q000145:classification / Q000175:diagnosis* / Q000473:pathology; D002291:Carcinoma, Papillary; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness / Q000175:diagnosis / Q000473:pathology; D000077273:Thyroid Cancer, Papillary; D013961:Thyroid Gland / Q000473:pathology*; D013964:Thyroid Neoplasms / Q000145:classification / Q000175:diagnosis* / Q000473:pathology; D016606:Thyroid Nodule / Q000145:classification / Q000175:diagnosis* / Q000473:pathology