title: Encapsulated follicular variant of papillary thyroid carcinoma: fine-needle aspiration with ultrasound and histologic correlation of 41 cases.
abstract: OBJECTIVE
  The encapsulated follicular variant of papillary carcinoma (FVPC) was recently reported to have genetic alterations and biological behavior closer to follicular adenoma/carcinoma than classic papillary carcinoma and unencapsulated FVPC. The objective of this study is to alert cytologists to this new subtype and to report our experience.
  
  
  METHODS
  Cytology of 41 cases of surgery-proven encapsulated FVPC was reviewed and correlated with histopathology and ultrasound findings. These cases were collected over 19 years from 188 aspirates reported as 'suspicious or atypical, cannot exclude FVPC' and from 245 aspirates reported as follicular neoplasm.
  
  
  RESULTS
  Thirteen aspirates had diffusely atypical nuclei, 20 aspirates had mixed normal and atypical nuclei, and 8 aspirates had no atypical nuclei. On histology, papillary nuclei were distributed focally in the second and third groups. Crowded, oval, clear nuclei occurred in nearly 80% of the cases, nuclear grooves occurred in 12.2%, and nuclear pseudoinclusions occurred in 4.9%. Capsular invasion without angioinvasion was present in 30% of encapsulated FVPCs, with angioinvasion in 17.5% and lymph node metastasis in 7.5%. Most encapsulated FVPCs were benign-appearing on ultrasound with round-to-oval, circumscribed nodules with a hypoechoic rim.
  
  
  CONCLUSIONS
  Encapsulated FVPC is more difficult to recognize on fine-needle aspiration and ultrasound than unencapsulated FVPC.
authors.affiliation: Department of Pathology and Laboratory Medicine, Weill Medical College of Cornell University, New York, NY, USA. gry2001@med.cornell.edu
authors.forename: Grace C H
authors.initials: GC
authors.lastname: Yang
authors.forename: Karen
authors.initials: K
authors.lastname: Fried
authors.forename: Tatiana V
authors.initials: TV
authors.lastname: Yakoushina
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Schreiner
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D044963:Biopsy, Fine-Needle; D018265:Carcinoma, Papillary, Follicular / Q000000981:diagnostic imaging* / Q000473:pathology*; D003581:Cytodiagnosis; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology*; D014463:Ultrasonography; D055815:Young Adult