Neuroendocrine tumors, Zollinger-Ellison syndrome

1. Big picture

Neuroendocrine tumors (NETs) are tumors arising from hormone-producing neuroendocrine cells. In gastroenterology, the most important group is gastroenteropancreatic neuroendocrine tumors (GEP-NETs), which may arise in the stomach, small intestine, appendix, rectum, colon, or pancreas.

The exam usually focuses on three clinical patterns:

1. Carcinoid syndrome → flushing + diarrhea + bronchospasm ± right-sided heart disease
2. Pancreatic NETs → hormone excess syndromes such as insulinoma, gastrinoma, VIPoma, glucagonoma, somatostatinoma
3. Zollinger–Ellison syndrome (ZES) → gastrinoma causing recurrent, multiple, refractory peptic ulcers + diarrhea

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