title: "Colloid-rich" follicular neoplasm/suspicious for follicular neoplasm thyroid fine-needle aspiration specimens: cytologic, histologic, and molecular basis for considering an alternate view.
abstract: BACKGROUND
  Typically, thyroid follicular neoplasm/suspicious for follicular neoplasm (FN/SFN) cases show moderate to marked cellularity and scant or absent colloid. Recently, cases have been noted with microfollicular cellularity in the background of moderate to abundant amount of colloid. The purpose of this study was to compare these "colloid-rich" FN/SFN cases to the typical FN/SFN cases.
  
  
  METHODS
  Thyroid cytology specimens with the features of FN/SFN were searched in cytopathology files from September 2008 to June 2012. Cases with absent or minimal colloid were designated "typical colloid-poor" FN/SFN and cases with moderate to abundant colloid were designated "colloid-rich" FN/SFN. From these cases, those with surgical pathology resection follow-up were identified. Cytologic, surgical pathology resection, and molecular features (BRAF, RAS, RET/PTC, and PAX8-PPARγ) were investigated for the typical colloid-poor FN/SFN cases and were compared with those of the colloid-rich FN/SFN cases.
  
  
  RESULTS
  Of 431 FN/SFN cases with surgical pathology resection follow-up, 360 (83.5%) cases showed features of typical colloid-poor FN/SFN and 71 (16.5%) cases showed features of colloid-rich FN/SFN. Papillary carcinoma was the most common malignant outcome for the 2 groups. Although the proportion of malignant outcome was similar for the 2 groups, the "colloid-rich" FN/SFN cases showed a greater proportion of nodular hyperplasia among the cases with benign outcome. In addition, the "colloid-rich" FN/SFN cases demonstrated a greater proportion of cases with a mutation.
  
  
  CONCLUSIONS
  Approximately one-sixth of cases of FN/SFN show "colloid-rich" features. Comparison to the typical colloid-poor FN/SFN demonstrated similar risk for malignancy but contrasting resection outcome and molecular characteristics.
authors.affiliation: Department of Pathology, University of Pittsburgh Medical Center-Presbyterian, Pittsburgh, Pennsylvania.
authors.forename: N Paul
authors.initials: NP
authors.lastname: Ohori
authors.forename: Jenna
authors.initials: J
authors.lastname: Wolfe
authors.forename: Steven P
authors.initials: SP
authors.lastname: Hodak
authors.forename: Shane O
authors.initials: SO
authors.lastname: LeBeau
authors.forename: Linwah
authors.initials: L
authors.lastname: Yip
authors.forename: Sally E
authors.initials: SE
authors.lastname: Carty
authors.forename: Umamaheswar
authors.initials: U
authors.lastname: Duvvuri
authors.forename: Karen E
authors.initials: KE
authors.lastname: Schoedel
authors.forename: Marina N
authors.initials: MN
authors.lastname: Nikiforova
authors.forename: Yuri E
authors.initials: YE
authors.lastname: Nikiforov
mesh_terms: D018263:Adenocarcinoma, Follicular / Q000235:genetics* / Q000473:pathology*; D000231:Adenocarcinoma, Papillary / Q000235:genetics / Q000473:pathology; D000368:Aged; D044963:Biopsy, Fine-Needle; D016009:Chi-Square Distribution; D015331:Cohort Studies; D003102:Colloids / Q000378:metabolism; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D009154:Mutation; D009361:Neoplasm Invasiveness / Q000473:pathology; D009367:Neoplasm Staging; D047495:PPAR gamma / Q000235:genetics; D012189:Retrospective Studies; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D013964:Thyroid Neoplasms / Q000235:genetics* / Q000473:pathology*
chemical_list: D003102:Colloids; D047495:PPAR gamma
keywords: BRAF; Bethesda Classification; PAX8-PPARγ; RAS; follicular neoplasm; thyroid