title: Cystic pancreatic neuroendocrine tumors: outcomes of preoperative endosonography-guided fine needle aspiration, and recurrence during long-term follow-up.
abstract: OBJECTIVE
  The role of endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) in the diagnosis and management of cystic pancreatic neuroendocrine tumors (PNETs) is unclear. We aimed to compare clinical/endosonographic characteristics of cystic with solid PNETs, determine diagnostic accuracy of preoperative EUS-FNA, and evaluate recurrence rates after resection.
  
  
  METHODS
  All patients with cystic or solid PNET confirmed by EUS-FNA between 2000 and 2014 were identified. A matched case-control study compared 50 consecutive patients with cystic PNETs with 50 consecutive patients with solid PNETs, matched by gender and age at diagnosis of index cystic PNET. We compared clinical/endosonographic characteristics, assessed diagnostic accuracy of preoperative EUS-FNA for identifying malignancy, and analyzed tumor-free survival of patients with cystic and solid PNETs.
  
  
  RESULTS
  Cystic PNETs tended to be larger than solid PNETs (mean 26.8 vs. 20.1 mm, P = 0.05), more frequently nonfunctional (96 % vs. 80 %, P = 0.03), and less frequently associated with multiple endocrine neoplasia type 1 (10 % vs. 28 %, P = 0.04). With surgical pathology as reference standard, EUS-FNA accuracies for malignancy of cystic and solid PNETs were 89.3 % and 90 %, respectively; cystic PNETs were less associated with metastatic adenopathy (22 % vs. 42 %, P = 0.03) and liver metastasis (0 % vs. 26 %, P < 0.001). Cystic fluid analysis (n = 13), showed benign cystic PNETs had low carcinoembryonic antigen (CEA), Ki-67 ≤ 2 %, and no loss of heterozygosity. Patients with cystic and solid PNETs had similar recurrence risk up to 5 years after complete resection.
  
  
  CONCLUSIONS
  Cystic PNETs have distinct clinical and EUS characteristics, but were associated with less aggressive biological behavior compared with solid PNETs. EUS-FNA is accurate for determining malignant potential on preoperative evaluation. Despite complete resection, recurrence is observed up to 5 years following surgery.
authors.affiliation: Indiana University School of Medicine, Indianapolis, Indiana, USA.
authors.forename: Wiriyaporn
authors.initials: W
authors.lastname: Ridtitid
authors.affiliation: Indiana University School of Medicine, Indianapolis, Indiana, USA.
authors.forename: Houssam
authors.initials: H
authors.lastname: Halawi
authors.affiliation: Indiana University School of Medicine, Indianapolis, Indiana, USA.
authors.forename: John M
authors.initials: JM
authors.lastname: DeWitt
authors.affiliation: Indiana University School of Medicine, Indianapolis, Indiana, USA.
authors.forename: Stuart
authors.initials: S
authors.lastname: Sherman
authors.affiliation: Indiana University School of Medicine, Indianapolis, Indiana, USA.
authors.forename: Julia
authors.initials: J
authors.lastname: LeBlanc
authors.affiliation: Indiana University School of Medicine, Indianapolis, Indiana, USA.
authors.forename: Lee
authors.initials: L
authors.lastname: McHenry
authors.affiliation: Indiana University School of Medicine, Indianapolis, Indiana, USA.
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Coté
authors.affiliation: Cleveland Clinic Abu Dhabi, Abu Dhabi, United Arab Emirates.
authors.forename: Mohammad A
authors.initials: MA
authors.lastname: Al-Haddad
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D061765:Endoscopic Ultrasound-Guided Fine Needle Aspiration; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local; D018358:Neuroendocrine Tumors / Q000175:diagnosis* / Q000601:surgery; D010180:Pancreatectomy; D010190:Pancreatic Neoplasms / Q000175:diagnosis* / Q000601:surgery; D011300:Preoperative Care; D012189:Retrospective Studies; D016896:Treatment Outcome