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Gastric neuroendocrine tumors (NETs)
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
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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
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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 performed
For high-grade tumors (ki-67 > 20% or > 20 mitoses/10 HPF), FDG-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
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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