Well-Differentiated Neuroendocrine Tumor, Ampulla

 Grade 3 tumors: Poorly differentiated neuroendocrine carcinoma (small or large cell type)

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Tumor in Ampullary RegionLow-power view shows a well-differentiated neuroendocrine neoplasm infiltrating the ampullary region. The overlying mucosa is attenuated and shows gastric foveolar metaplasia image .

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Histologic FeaturesTumor cells are typically uniform with round nuclei, salt and pepper chromatin, inconspicuous nuclei, and moderate amounts of eosinophilic cytoplasm. Focal glandular formation image is noted. Mitotic figures are difficult to find.
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Psammoma BodiesWell-differentiated neuroendocrine neoplasm of the ampulla shows extensive glandular formation. Psammomatous calcifications are noted in the lumina of some of the glands image. These features are more commonly seen in somatostatin-producing tumors.
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Ki-67 IndexWell-differentiated neuroendocrine neoplasm of the ampulla shows positive immunostain for Ki-67 in ∼ 5% of tumor cells. The tumor is thus graded as intermediate (grade 2), even though the mitotic rate is < 2 per 10 HPF.

TERMINOLOGY

Abbreviations

• Well-differentiated neuroendocrine neoplasm (WDNEN)

Synonyms

• Well-differentiated neuroendocrine tumor
• Carcinoid tumor (not preferred)

Definitions

• Low- to intermediate-grade neoplasms with predominantly neuroendocrine differentiation arising in ampulla of Vater and periampullary region

ETIOLOGY/PATHOGENESIS

Disease Association

• Neurofibromatosis type 1
image Somatostatin-producing tumors are most common
• Multiple endocrine neoplasia type 1
image Gastrin-producing tumors are most common
• Helicobacter pylori infection

CLINICAL ISSUES

Epidemiology

• Incidence
image < 1% of all gastrointestinal neuroendocrine neoplasms
image < 2% of all tumors of ampullary region
Apr 20, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Well-Differentiated Neuroendocrine Tumor, Ampulla

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