Neuroendocrine Tumors, Gastric

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

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

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

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