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Key Features

  • Gastric neuroendocrine tumors (NETs)

    • Rare

    • Account for < 1% of gastric neoplasms

    • Sporadic or secondary to chronic hypergastrinemia

  • Gastric NETs secondary to chronic hypergastrinemia

    • Type 1 gastric NETs occur in association with pernicious anemia (75% of cases)

    • Type 2 gastric NETs occur with Zollinger-Ellison syndrome in multiple endocrine neoplasia type 1 (MEN 1) (5%)

    • Tend to be multicentric, < 1 cm, with low potential for metastatic spread to the liver and thus unlikely to cause the carcinoid syndrome

  • Type 3 gastric NETs arise sporadically, independent of gastrin production, and account for up to 20% of all gastric NETs

Clinical Findings

  • Most asymptomatic, detected incidentally during endoscopy

  • May ulcerate, causing occult GI bleeding and anemia

  • Most sporadic gastric carcinoids are solitary, > 2 cm in size, and have a strong propensity for hepatic or pulmonary metastases

Diagnosis

  • Initial diagnostic work-up includes serum gastrin level, upper endoscopy, and endoscopic ultrasound

  • Gastrin level should be obtained after the patient has stopped taking proton pump inhibitors for 1 week

  • For low-grade tumors (ki-67 < 3% or < 2 mitoses/10 HPF), somatostatin receptor-based imaging (somatostatin receptor scintigraphy or gallium-68 dotatate PET/CT) should be considered

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

  • Serum vitamin B12 and intrinsic factor antibody levels should be obtained to exclude pernicious anemia

  • In type 2 carcinoids associated with Zollinger-Ellison syndrome in MEN 1, chromosomal loss of 11q13 has been reported

  • CT or MRI should be obtained to evaluate for metastatic disease

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

Treatment

  • Small lesions: endoscopic resection followed by periodic endoscopic surveillance or with observation

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

  • Octreotide therapy may be appropriate for patients with underlying gastrinoma and Zollinger-Ellison syndrome

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

  • Localized sporadic NETs should be treated with radical gastrectomy and regional lymphadenectomy

  • Sandostatin analogs may provide symptomatic relief for patients with functional gastric NETs

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

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