title: Comparison of 5-tiered and 6-tiered diagnostic systems for the reporting of thyroid cytopathology: a multi-institutional study.
abstract: BACKGROUND
  At present, thyroid fine-needle aspiration (FNA) specimens are diagnosed using a tiered classification scheme, with the most popular of these being the 5-tiered and 6-tiered systems. In this study, the authors present their institutional experiences using these 2 different systems and evaluate their efficacy based on the surgical follow-up.
  
  
  METHODS
  Thyroid FNA specimens and their corresponding surgical resection specimens were collected between 2007 and 2009. The following diagnostic categories are used in both systems: unsatisfactory/nondiagnostic, benign, follicular neoplasm/suspicious for follicular neoplasm, suspicious for malignancy, and malignant. An additional category termed atypia of undetermined significance/follicular lesion of undetermined significance was used for atypical cases in the 6-tiered system. Statistical analysis was performed by comparing the different diagnostic categories.
  
  
  RESULTS
  The case cohort included a total of 7686 thyroid FNA specimens representing 3962 nodules and 3724 nodules, respectively, in the 5-tiered and 6-tiered systems. Negative predictive values for the benign categories (96.9% vs 97.5%; P = 1) and positive predictive values for both the follicular neoplasm categories (26.5% vs 32.1%; P = .2531) and the malignant categories (99.1% vs 99.4%; P = 1) were similar. The most significant differences between the 5-tiered and 6-tiered systems were the percentage of cases classified as benign (83.9% vs 55.4%; P < .0001) and as follicular neoplasms (4.6% vs 23.8%; P < .0001). It is interesting to note that fewer patients were referred for surgery in the 5-tiered system compared with the 6-tiered one (9.1% vs 36.5%; P < .0001).
  
  
  CONCLUSIONS
  Use of either the 5-tiered or 6-tiered reporting systems for thyroid FNA specimens can potentially affect the clinical management of patients with thyroid nodules.
authors: Institute of Pathology, Locarno, Switzerland. massimo.bongiovanni@ti.ch
authors: Massimo
authors: M
authors: Bongiovanni
authors: Stefano
authors: S
authors: Crippa
authors: Zubair
authors: Z
authors: Baloch
authors: Simonetta
authors: S
authors: Piana
authors: Alessandra
authors: A
authors: Spitale
authors: Fabio
authors: F
authors: Pagni
authors: Luca
authors: L
authors: Mazzucchelli
authors: Camillo
authors: C
authors: Di Bella
authors: William
authors: W
authors: Faquin
mesh_terms: D018263:Adenocarcinoma, Follicular / Q000473:pathology* / Q000601:surgery; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D044963:Biopsy, Fine-Needle; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D013961:Thyroid Gland / Q000473:pathology* / Q000601:surgery; D013964:Thyroid Neoplasms / Q000473:pathology* / Q000601:surgery; D055815:Young Adult