title: Cystic pancreatic endocrine tumor: a variant commonly confused with cystic adenocarcinoma.
abstract: BACKGROUND
  Most cystic pancreatic neoplasms are currently evaluated by an endoscopic ultrasound-guided fine-needle aspiration biopsy (FNAB). In the authors' experience, FNAB of cystic pancreatic endocrine tumors (PETs) frequently causes diagnostic difficulties, partly because of unexpected overlapping features with cystic ductal adenocarcinomas.
  
  
  METHODS
  The authors identified 5 histologically confirmed cystic PETs that were evaluated by FNAB and compared their cytomorphologic features to cystic ductal adenocarcinomas (n = 5) and solid PETs (n = 39) of the pancreas.
  
  
  RESULTS
  Cytologically, 2 of the aspirates of cystic PETs were devoid of tumor cells whereas the other 3 were variably cellular and composed of cohesive aggregates of monomorphic cellular elements with variably coarse chromatin. Tumor necrosis and nuclear membrane irregularities were not identified in cystic PETs. Alternatively, in contrast to PETs, cystic ductal adenocarcinomas were characterized by nuclear pleomorphism, nuclear membrane irregularities, and tumor necrosis.
  
  
  CONCLUSIONS
  Given the clinical implications, awareness of cystic PETs and their deceptive cytologic features would assist in distinguishing these lesions from cystic ductal adenocarcinomas.
authors.affiliation: Department of Pathology, Cytology and Gastrointestinal Pathology Service, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA. vdeshpande@partners.org
authors.forename: Vikram
authors.initials: V
authors.lastname: Deshpande
authors.forename: Gregory Y
authors.initials: GY
authors.lastname: Lauwers
mesh_terms: D000230:Adenocarcinoma / Q000175:diagnosis / Q000473:pathology*; D000368:Aged; D044963:Biopsy, Fine-Needle; D021441:Carcinoma, Pancreatic Ductal / Q000175:diagnosis / Q000473:pathology*; D003937:Diagnosis, Differential; D006801:Humans; D008297:Male; D008875:Middle Aged; D010190:Pancreatic Neoplasms / Q000175:diagnosis / Q000473:pathology*