title: Outcome of Subclassification of Indeterminate (Thy-3) Thyroid Cytology into Thy-3a and Thy-3f.
abstract: OBJECTIVE
  The British Thy system is a widely used classification system for reporting thyroid fine-needle aspiration (FNA) cytology. The Royal College of Pathologists in 2009 recommended the subdivision of the Thy-3 (indeterminate) category into Thy-3a (atypia) and Thy-3f (follicular neoplasm). Our objective was to examine the malignancy rates of Thy-3a and Thy-3f cases at our institution and to investigate whether the risk of malignancy in Thy-3a cases is reduced by FNA on a different occasion showing benign cytology.
  
  
  METHODS
  This is a retrospective study of 748 thyroid nodules undergoing 1,032 FNAs, with indeterminate (Thy-3) cytology subdivided into Thy-3a and Thy-3f. Cases were correlated with final histology in surgical cases. Incidental carcinomas occurring outside the biopsied nodule were discounted.
  
  
  RESULTS
  A total of 109 nodules had a final cytological diagnosis of Thy-3a, of which 67 underwent surgery, with an incidence of malignancy of 13.4% (9/67); 90 nodules had a final cytological diagnosis of Thy-3f, of which 84 underwent surgery, with an incidence of malignancy of 17.9% (15/84). The difference in malignancy rates was not significant (p = 0.51). The incidence of malignancy in nodules with benign and Thy-3a cytology on separate occasions was not significantly different from cases with a single Thy-3a cytology.
  
  
  CONCLUSIONS
  Thyroid nodules with Thy-3a cytology have a slightly lower risk of malignancy than Thy-3f cases. However, the difference is not significant and does not appear to be reduced by FNA on a separate occasion showing benign cytology. Management decisions for patients with Thy-3a cytology should be taken carefully to avoid missing cancers.
authors.affiliation: Department of Otolaryngology - Head and Neck Surgery, Cork, Ireland.
authors.forename: Catherine
authors.initials: C
authors.lastname: Brophy
authors.affiliation: Department of Otolaryngology - Head and Neck Surgery, Cork, Ireland.
authors.forename: Rania
authors.initials: R
authors.lastname: Mehanna
authors.affiliation: Department of Cytopathology, Cork University Hospital, Cork, Ireland.
authors.forename: Julie
authors.initials: J
authors.lastname: McCarthy
authors.affiliation: Department of Endocrinology, Cork University Hospital, Cork, Ireland.
authors.forename: Antoinette
authors.initials: A
authors.lastname: Tuthill
authors.affiliation: Department of Endocrinology, South Infirmary Victoria University Hospital, Cork, Ireland.
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Murphy
authors.affiliation: Department of Otolaryngology - Head and Neck Surgery, Cork, Ireland.
authors.forename: Patrick
authors.initials: P
authors.lastname: Sheahan
keywords: Atypia of uncertain significance; Cytology; Follicular lesion of uncertain significance; Thy; Thy-3; Thyroid
references.citation: CA Cancer J Clin. 2009 Mar-Apr;59(2):99-110
references.pmid: 19278960
references.citation: Acta Cytol. 2011;55(6):499-506
references.pmid: 22156457
references.citation: Acta Cytol. 2011;55(6):492-8
references.pmid: 22156456
references.citation: J Thyroid Res. 2013;2013:250347
references.pmid: 23634318
references.citation: Cytojournal. 2008 Apr 07;5:6
references.pmid: 18394201
references.citation: Cytopathology. 2013 Dec;24(6):385-90
references.pmid: 23078633
references.citation: Ann Surg Oncol. 2014 Jul;21(7):2326-31
references.pmid: 24566858
references.citation: Cancer. 2013 Apr 15;119(8):1495-502
references.pmid: 23280049
references.citation: N Engl J Med. 2012 Aug 23;367(8):705-15
references.pmid: 22731672
references.citation: Diagn Cytopathol. 2012 May;40(5):410-5
references.pmid: 22508675
references.citation: Ann Surg Oncol. 2012 Jan;19(1):45-51
references.pmid: 21633868
references.citation: Br J Surg. 2009 Dec;96(12):1400-5
references.pmid: 19918854
references.citation: Thyroid. 2014 May;24(5):832-9
references.pmid: 24341462
references.citation: Clin Endocrinol (Oxf). 2014 May;80(5):735-42
references.pmid: 24117478
references.citation: Am J Clin Pathol. 2010 Sep;134(3):450-6
references.pmid: 20716802
references.citation: Cancer. 2007 Oct 25;111(5):306-15
references.pmid: 17680588
references.citation: Cytopathology. 2014 Feb;25(1):39-44
references.pmid: 23438201
references.citation: J Clin Endocrinol Metab. 2009 Jun;94(6):2092-8
references.pmid: 19318445
references.citation: Diagn Cytopathol. 2008 Jun;36(6):425-37
references.pmid: 18478609
references.citation: J Otolaryngol Head Neck Surg. 2010 Apr;39(2):167-70
references.pmid: 20211103
references.citation: Laryngoscope. 2013 May;123(5):1305-9
references.pmid: 23293053
references.citation: Acta Cytol. 2011;55(6):507-11
references.pmid: 22156458
references.citation: Acta Cytol. 2009 Sep-Oct;53(5):517-23
references.pmid: 19798878
references.citation: Endocrinol Metab Clin North Am. 2007 Sep;36(3):707-35, vi
references.pmid: 17673125
references.citation: Diagn Cytopathol. 2010 Oct;38(10):731-9
references.pmid: 20049964
references.citation: World J Surg. 2012 Jan;36(1):69-74
references.pmid: 22057754
references.citation: Thyroid. 2010 Oct;20(10):1077-83
references.pmid: 20883171
references.citation: Diagn Cytopathol. 2009 Oct;37(10):710-4
references.pmid: 19373907
references.citation: Acta Cytol. 2011;55(6):570-5
references.pmid: 22156468
references.citation: Thyroid. 2003 Apr;13(4):381-7
references.pmid: 12804106
references.citation: Ann Surg Oncol. 2013 Jan;20(1):60-5
references.pmid: 22941160
references.citation: Surgery. 2011 Dec;150(6):1234-41
references.pmid: 22136846
references.citation: J Clin Endocrinol Metab. 2011 Nov;96(11):3390-7
references.pmid: 21880806
references.citation: Clin Endocrinol (Oxf). 2014 Jul;81 Suppl 1:1-122
references.pmid: 24989897
references.citation: Thyroid. 2012 Dec;22(12):1251-6
references.pmid: 22962940
references.citation: Ann Surg Oncol. 1996 Nov;3(6):534-8
references.pmid: 8915484