Neuroendocrine neoplasms
Well differentiated neuroendocrine tumor WHO grade 1 / 2 (carcinoid)

Author: Deepali Jain, M.D. (see Authors page)

Revised: 22 December 2017, last major update August 2012

Copyright: (c) 2002-2017,, Inc.

PubMed Search: Well differentiated neuroendocrine tumor G1 G2 pancreas

Cite this page: Jain, D. Well differentiated neuroendocrine tumor WHO grade 1 / 2 (carcinoid). website. Accessed August 20th, 2018.
Definition / general
  • Rare, arise from Kultschitsky (serotonin secreting) cells normally present in pancreas
  • Classified using similar criteria as other GI neuroendocrine neoplasms (IARC: 8249 / 3 Neuroendocrine Tumor, Grade 2 [Accessed 22 December 2017])
  • Well differentiated: cells with features similar to normal gut endocrine cell, expressing general markers of neuroendocrine differentiation (usually diffuse and intense chromogranin A and synaptophysin) and hormones (usually intense but not necessarily diffuse) according to site, with mild to moderate nuclear atypia and a low number of mitoses
  • G1 (NET G1): mitotic count < 2/10 HPF or ≤ 2% Ki67 index
  • G2 (NET G2): mitotic count 2 - 20/10 HPF or 3 - 20% Ki67 index
Clinical features
  • Acceptable to supplement diagnosis to reflect the corresponding cell type (example: alpha cell / glucagon producing NET, beta cell / insulin producing NET, G cell / gastrin producing NET) but recommended to NOT use specific functional terms (glucagonoma, insulinoma, gastrinoma) unless hormonal syndrome exists
  • May be associated with carcinoid syndrome (flushing, diarrhea)
Gross images

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Invasion of large vessel

Tumor is well demarcated from surrounding parenchyma

Microscopic (histologic) images

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Gastric carcinoid in MEN1

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Tumor cells have salt and pepper chromatin

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Organoid pattern characterized by nests and sheets

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Positive stains
  • For metastatic neuroendocrine tumors, NESP55+ and PDX1+, in the presence of negative CDX2 and TTF1, is 97% specific for pancreatic origin (Am J Surg Pathol 2009;33:626)
  • Strongly argentaffinic (contains catecholamines, indolamines or related substance that reduces silver and other metallic salts to metallic silver, staining brown or black) - includes Fontana-Masson, Schmorl
Negative stains
Electron microscopy images

Images hosted on PathOut server:

ECL type vesicular granules (left) and solid granules (right) with cerebroid punctate structure