title: False-positive cytopathology results for papillary thyroid carcinoma: A trap for thyroid surgeons.
abstract: OBJECTIVE
  Current preoperative diagnosis of thyroid nodules remains imperfect despite recent advances in cytopathology and molecular diagnostics. False positivity in preoperative fine-needle aspiration cytology (FNAC) may lead to overtreatment of patients, including total thyroidectomy, and sometimes to lawsuits for misdiagnosis and malpractice. In this study, we analysed clinical characteristics and pathologic findings in patients with false positivity for papillary thyroid carcinoma (PTC) in FNAC.
  
  
  METHODS
  We retrospectively reviewed permanent pathology results from 3788 patients who underwent thyroid surgery. Among them, 48 patients had lesions that were deemed suspicious or positive (Bethesda class V or VI) for PTC in preoperative FNAC. We reviewed clinic-pathologic data, radiologic findings and surgical planning in these patients.
  
  
  RESULTS
  The prevalence of pathologic thyroiditis was significantly higher among patients with false-positive FNAC results than in those with confirmed PTC (54.2% vs 9.2%, P<.001). The analysis of the permanent pathology reports showed that 26 patients had chronic lymphocytic thyroiditis and 22 patients had no evidence of thyroiditis. Among the patients without pathologic thyroiditis, 19 patients (86.4%) had nodular hyperplasia and three (13.6%) had follicular adenoma, while among the patients with pathologic thyroiditis, seven (26.9%) had no nodule, 14 (53.8%) had nodular hyperplasia, two (7.7%) had hyalinized nodules, two (7.7%) had follicular adenoma and one (3.8%) had a hyalinizing trabecular tumour. In 42 patients, the extent of surgery (total thyroidectomy or hemithyroidectomy) was to be determined according to the intra-operative frozen section biopsy results. Among them, four (10.5%) had inconclusive frozen section results, and 38 (90.5%) had benign results on frozen section.
  
  
  CONCLUSIONS
  Patient counselling about the possibility of false positivity is still important. And the presence of thyroiditis might create confusion in the interpretation of cytopathologic results.
authors.affiliation: Department of Otorhinolaryngology-Head and Neck Surgery and Biomedical Research Institute, Pusan National University Hospital, Busan, Korea.
authors.forename: K-I
authors.initials: KI
authors.lastname: Yi
authors.affiliation: Department of Pathology, Pusan National University Hospital, Busan, Korea.
authors.forename: S
authors.initials: S
authors.lastname: Ahn
authors.affiliation: Department of Pathology, Pusan National University Hospital, Busan, Korea.
authors.forename: D Y
authors.initials: DY
authors.lastname: Park
authors.affiliation: Department of Otorhinolaryngology-Head and Neck Surgery, Pusan National University School of Medicine, Yangsan, Gyeongnam, Korea.|Department of Otorhinolaryngology-Head and Neck Surgery, Pusan National University Yangsan Hospital, Yangsan, Gyeongnam, South Korea.
authors.forename: J-C
authors.initials: JC
authors.lastname: Lee
authors.affiliation: Department of Otorhinolaryngology-Head and Neck Surgery and Biomedical Research Institute, Pusan National University Hospital, Busan, Korea.|Department of Otorhinolaryngology-Head and Neck Surgery, Pusan National University School of Medicine, Yangsan, Gyeongnam, Korea.
authors.forename: B-J
authors.initials: BJ
authors.lastname: Lee
authors.affiliation: Department of Otorhinolaryngology-Head and Neck Surgery and Biomedical Research Institute, Pusan National University Hospital, Busan, Korea.|Department of Otorhinolaryngology-Head and Neck Surgery, Pusan National University School of Medicine, Yangsan, Gyeongnam, Korea.
authors.forename: S-G
authors.initials: SG
authors.lastname: Wang
authors.affiliation: Department of Otorhinolaryngology-Head and Neck Surgery and Biomedical Research Institute, Pusan National University Hospital, Busan, Korea.|Department of Otorhinolaryngology-Head and Neck Surgery, Pusan National University School of Medicine, Yangsan, Gyeongnam, Korea.
authors.forename: W
authors.identifier: http://orcid.org/0000-0001-7292-9474
authors.initials: W
authors.lastname: Cha
mesh_terms: D000328:Adult; D000368:Aged; D044963:Biopsy, Fine-Needle; D002291:Carcinoma, Papillary / Q000473:pathology* / Q000601:surgery; D003951:Diagnostic Errors; D005189:False Positive Reactions; D005260:Female; D005629:Frozen Sections; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D000077273:Thyroid Cancer, Papillary; D013964:Thyroid Neoplasms / Q000473:pathology* / Q000601:surgery; D016606:Thyroid Nodule / Q000473:pathology; D013965:Thyroidectomy; D013966:Thyroiditis / Q000473:pathology
keywords: Papillary thyroid carcinoma; diagnostic accuracy; false positivity; fine-needle aspiration cytology; intra-operative frozen section