title: False positive endoscopic ultrasound fine needle aspiration cytology: incidence and risk factors.
abstract: OBJECTIVE
  It is broadly accepted that the false positive (FP) rate for endoscopic ultrasound fine needle aspiration (EUS FNA) is 0-1%. It was hypothesised that the FP and false suspicious (FS) rates for EUS FNA are greater than reported. A study was undertaken to establish the rate and root cause of discordant interpretation.
  
  
  METHODS
  Using a prospectively maintained endoscopic database, cytohistological discordant EUS FNA examinations from 30 July 1996 to 31 December 2008 were identified retrospectively.
  
  
  METHODS
  Tertiary referral centre.
  
  
  METHODS
  Discordant FNA was defined by positive or suspicious FNA cytology in the absence of malignancy or neoplasm in the subsequent surgical pathology specimen, specifically in the absence of neoadjuvant therapy. Three cytopathologists conducted a blinded review of randomised discordant and matched specimens.
  
  
  RESULTS
  FNA was performed in 5667/18 066 (31.4%) patients undergoing EUS, of whom 2547 had cytology results interpreted as 'positive' or 'suspicious' or 'atypical' for malignancy or neoplasm. Subsequent surgical resection without prior neoadjuvant therapy was performed in 377 patients with positive or suspicious cytology. The FP rate was 20/377 (5.3%) and increased to 27/377 (7.2%) when FS cases were included. The incidence of discordance was consistent over time (1996-2002: 10/118 (8.6%) vs 2003-2008: 17/259 (6.6%); p=0.5) and was higher in non-pancreatic FNA (15%) than pancreatic FNA (2.2%; p=0.0001). Two-thirds of the non-pancreatic FP cases involved sampling of perioesophageal or perirectal nodes in patients with luminal neoplasms or Barrett's oesophagus. Following pathological re-review, discordance was attributed to translocated cell contamination/sampling error (50%) or cytopathologist interpretive error (50%).
  
  
  CONCLUSIONS
  These findings refute the accepted paradigm that FP cytology rarely occurs with EUS FNA. Further investigation revealed that FP FNA developed secondary to endosonographer technique or initial cytological misinterpretation, and is particularly likely when perioesophageal or perirectal nodes are aspirated in the setting of a luminal neoplasm or Barrett's oesophagus. Further study is needed to determine the significance of these findings and potential impact on the performance of FNA and patient outcomes.
authors.affiliation: Division of Gastroenterology and Hepatology, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, USA.
authors.forename: Ferga C
authors.initials: FC
authors.lastname: Gleeson
authors.forename: Benjamin R
authors.initials: BR
authors.lastname: Kipp
authors.forename: Jill L
authors.initials: JL
authors.lastname: Caudill
authors.forename: Jonathan E
authors.initials: JE
authors.lastname: Clain
authors.forename: Amy C
authors.initials: AC
authors.lastname: Clayton
authors.forename: Kevin C
authors.initials: KC
authors.lastname: Halling
authors.forename: Michael R
authors.initials: MR
authors.lastname: Henry
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Rajan
authors.forename: Mark D
authors.initials: MD
authors.lastname: Topazian
authors.forename: Kenneth K
authors.initials: KK
authors.lastname: Wang
authors.forename: Maurits J
authors.initials: MJ
authors.lastname: Wiersema
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Levy
mesh_terms: D044963:Biopsy, Fine-Needle / Q000592:standards* / Q000706:statistics & numerical data; D004067:Digestive System Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D019160:Endosonography / Q000592:standards / Q000706:statistics & numerical data; D004812:Epidemiologic Methods; D005189:False Positive Reactions; D006801:Humans; D008910:Minnesota; D010190:Pancreatic Neoplasms / Q000473:pathology; D018084:Ultrasonography, Interventional / Q000592:standards / Q000706:statistics & numerical data; D016526:Workload