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Neuroendocrine tumors

NET G1 / Carcinoid tumors

Reviewer: Deepali Jain, M.D. (see Reviewers page)
Revised: 28 November 2012, last major update August 2012
Copyright: (c) 2001-2012, PathologyOutlines.com, Inc.


● Rare, arise from Kultschitsky (serotonin secreting) cells normally present in pancreas


● Classified using similar criteria as other GI neuroendocrine neoplasms (WHO)
● 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

Large tumor with hemorrhage and degeneration

Invasion of large vessel

Tumor is well demarcated from surrounding parenchyma

Micro images

Trabecular and nesting patterns

Tumor cells have salt and pepper chromatin

A/B: H&E; C: chromogranin, D: keratin, E: NSE, F: synaptophysin

Organoid pattern characterized by nests and sheets


Stomach: gastric carcinoid in MEN1 associated Zollinger Ellinger syndrome - mosaic-like pattern of solid cords and microlobules separated by very thin stromal septa.

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's

Negative stains

● PAX8 (Histochem Cell Biol 2011;136:595-previous PAX8+ tumors based on cross-reactivity of polyclonal antibodies)

Electron microscopy images

Stromach: argyrophil gastric carcinoid - ECL-type vesicular granules (left) and solid granules (right) with cerebroid punctate structure (atypical ECL cell granules?) in gastric carcinoids

End of Pancreas > Tumors > Carcinoid tumors

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