title: Malignant cell contamination may lead to false-positive findings at endosonographic fine needle aspiration for tumor staging.
abstract: OBJECTIVE
  Endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) of lymph nodes is used for staging of gastrointestinal malignancies. False-positive rates of 5 % - 7 % are not well understood. Elements of EUS examinations that contribute to false-positive cytological findings were investigated.
  
  
  METHODS
  13 patients undergoing EUS staging of gastrointestinal luminal malignancy were consecutively enrolled together with 3 patients with extraluminal tumors (pancreas, lung) defined as controls. After EUS, cellular debris and fluid were collected from the FNA needle catheter, instrument channel, and endoscope tip for cytologic and histologic investigation.
  
  
  RESULTS
  6 of 13 patients (46 %) had malignant cells contaminating the FNA needle catheter, instrument channel, or endoscope tip. Malignant cells were present in the instrument channel in 5 cases (38 %), exterior tip of echoendoscope in 4 (31 %) and needle catheter in 2 (15 %).
  
  
  CONCLUSIONS
  Echoendoscopes used for FNA in patients with luminal tumors are at risk for malignant cell contamination of the instrument channel, FNA needle catheter, and echoendoscope tip. FNA needle contamination can contribute to false-positive findings.
authors.affiliation: Division of Gastroenterology University of California San Diego, La Jolla, California, USA.
authors.forename: Wilson T-Y
authors.initials: WT
authors.lastname: Kwong
authors.affiliation: Division of Gastroenterology Scripps Clinic, La Jolla, California, USA.
authors.forename: Walter J
authors.initials: WJ
authors.lastname: Coyle
authors.affiliation: Department of Pathology University of California San Diego, La Jolla, California, USA.
authors.forename: Farnaz
authors.initials: F
authors.lastname: Hasteh
authors.affiliation: Department of Pathology University of California San Diego, La Jolla, California, USA.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Peterson
authors.affiliation: Division of Gastroenterology University of California San Diego, La Jolla, California, USA.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Savides
authors.affiliation: Division of Gastroenterology University of California San Diego, La Jolla, California, USA.
authors.forename: Mary L
authors.initials: ML
authors.lastname: Krinsky
mesh_terms: D000230:Adenocarcinoma / Q000000981:diagnostic imaging / Q000473:pathology*; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging / Q000473:pathology*; D004067:Digestive System Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology*; D061765:Endoscopic Ultrasound-Guided Fine Needle Aspiration / Q000295:instrumentation; D005189:False Positive Reactions; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology*; D009367:Neoplasm Staging; D011446:Prospective Studies; D016037:Single-Blind Method