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For further information, see CMDT Part 41-12: Gastric Neuroendocrine Tumors

KEY FEATURES

  • Gastric neuroendocrine tumors (gNETs)

    • Account for < 1% of gastric neoplasms and are generally slow-growing tumors

    • Occur sporadically or secondary to chronic hypergastrinemia

  • Tumors are classified into 4 types

    • Types 1 and 2 account for the majority of gNETs

    • Types 3 and 4 account for up to 20% of gNETs

CLINICAL FINDINGS

  • Types 1 and 2 gNETs are caused by hypergastrinemia

    • Type 1 associated with pernicious anemia (75%)

      • Chronic atrophic gastritis

      • Gastric achlorhydria

    • Consequent secondary hypergastrinemia

    • Type 2 associated with Zollinger-Ellison syndrome (5%)

  • Types 3 and 4 gNETs arise sporadically

    • Are independent of gastrin production

    • Account for ∼20% of gNETS

    • Caused by a gastrin-secreting NET (gastrinoma) most commonly located in the pancreas or duodenum

DIAGNOSIS

  • Type 1 gNETs

    • Initial diagnostic work-up includes

      • CBC

      • Serum vitamin B12 level

      • Intrinsic factor antibody to help diagnose pernicious anemia

      • Serum gastrin level (≥ 1 week after the patient has stopped taking protein pump inhibitors)

    • Staging involves upper endoscopy and endoscopic ultrasound

    • For low-grade tumors (proliferation index of Ki-67 < 3% or mitotic index of < 2 mitoses/10 high-power fields [HPF] on histopathological analysis), somatostatin receptor-based imaging (somatostatin receptor scintigraphy or gallium-68 dotatate PET-CT) should be performed

    • For high-grade tumors (Ki-67 > 20% or > 20 mitoses/10 HPF), FDG-PET/CT is preferred to evaluate the extent of disease

  • Type 2 gNETS

    • Caused by a gastrin-secreting NET (gastrinoma)

    • Most commonly located in the pancreas or duodenum

    • Occur almost exclusively in patients with multiple endocrine neoplasia type 1 (MEN 1), in which chromosomal loss of 11q13 has been reported

  • Types 3 and 4 gNETs

    • Are most often solitary and > 2 cm

    • Have a strong propensity for hepatic or pulmonary metastases

    • Associated with carcinoid syndrome at initial presentation

    • Gallium68 dotatate PET/CT scan should be obtained to evaluate for metastatic disease

  • Advanced, low-grade gastric NETs can be monitored with serial scans, if asymptomatic

TREATMENT

  • Type 1 and 2 gNETs:

    • Small type 1 and 2 gNETs: endoscopic resection followed by endoscopic surveillance every 6–12 months, or with observation

    • Antrectomy reduces serum gastrin levels and may lead to regression of small tumors

    • Type 2 gNETs with underlying gastrinoma and Zollinger-Ellison syndrome may be treated with somatostatin analog (octreotide) therapy

    • Patients with tumors > 2 cm in size should undergo endoscopic or surgical resection

  • Localized sporadic type 3 and 4 gNETs should be treated with partial or total gastrectomy and regional lymphadenectomy

  • Octreotide may provide symptomatic relief for patients with gNETs that are functional (carcinoid syndrome)

  • Advanced high-grade gastric neuroendocrine carcinomas are treated in a fashion similar to small cell lung cancers

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