title: An overview of practical issues in the diagnosis of gastroenteropancreatic neuroendocrine pathology.
abstract: BACKGROUND
  Although somewhat uncommon, neuroendocrine tumors of the gastrointestinal tract and pancreas have come under scrutiny in recent times. With advances in imaging techniques, more of these tumors are being removed and sent for pathologic evaluation. It is important for the diagnostic pathologist to be aware of recent developments in this field.
  
  
  OBJECTIVE
  This overview focuses on nomenclature/terminology, classification, practical issues related to recent developments in immunohistochemical markers that aid diagnosis and may relate to prognosis, and molecular advances.
  
  
  METHODS
  Currently available literature and personal experience in the field of neuroendocrine pathology.
  
  
  CONCLUSIONS
  The preferred terminology is neuroendocrine/tumor/carcinoma and it is recommended that the World Health Organization classification be used, taking note of the site variations that may occur. A large number of immunohistochemical markers are available but a core panel that is relevant to the site should be used. Cytokeratin 19 positivity is an independent marker of aggressive behavior in pancreatic neuroendocrine tumors. Gastrointestinal neuroendocrine tumors arise via the CpG island methylator phenotype pathway, whereas their pancreatic counterparts arise as a result of chromosomal instability. The MEN1 gene is implicated in both syndromic and sporadic forms of these tumors.
authors.affiliation: Department of Pathology, University Health Network/University of Toronto, Toronto, Ontario, Canada. runjan.chetty@uhn.on.ca
authors.forename: Runjan
authors.initials: R
authors.lastname: Chetty
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis; D005770:Gastrointestinal Neoplasms / Q000737:chemistry / Q000145:classification / Q000235:genetics* / Q000473:pathology*; D006801:Humans; D007150:Immunohistochemistry; D008967:Molecular Biology / Q000379:methods; D018358:Neuroendocrine Tumors / Q000737:chemistry / Q000145:classification / Q000235:genetics* / Q000473:pathology*; D010190:Pancreatic Neoplasms / Q000737:chemistry / Q000145:classification / Q000235:genetics* / Q000473:pathology*; D009626:Terminology as Topic
chemical_list: D014408:Biomarkers, Tumor