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Pancreas

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.

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

Terminology
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● 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
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● 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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Large tumor with hemorrhage and degeneration


Invasion of large vessel

 
Tumor is well demarcated from surrounding parenchyma

Micro images
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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


Serotonin+


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

Electron microscopy images
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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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