gastrinomas

Gastrinomas are neuroendocrine tumors that secrete the hormone gastrin, causing excess stomach acid production and Zollinger-Ellison syndrome (ZES). They are relatively rare and can occur sporadically or in association with multiple endocrine neoplasia type 1 (MEN1). Most gastrinomas arise in the head of the pancreas or in the duodenum; other sites include lymph nodes and, less often, other parts of the gastrointestinal tract.

Excess gastrin stimulates gastric acid secretion, leading to peptic ulcers that are often multifocal and distal, as well as abdominal pain and diarrhea. Ulcers may be refractory to standard therapy and can lead to complications such as bleeding or perforation. Diarrhea is common and can be severe due to acid injury inactivation of pancreatic enzymes and bicarbonate loss.

Diagnosis starts with clinical suspicion in patients with difficult-to-treat peptic ulcers or chronic diarrhea. Fasting serum gastrin is measured; values above a high threshold (>1000 pg/mL) are highly suggestive of a gastrinoma, while intermediate elevations require a secretin stimulation test, in which a paradoxical rise in gastrin supports the diagnosis. Localization and staging use imaging such as contrast-enhanced CT or MRI, endoscopic ultrasound, and functional imaging with somatostatin receptor scintigraphy or Ga-68 DOTATATE PET/CT, which help identify primary tumors and metastases.

Treatment focuses on controlling acid hypersecretion and removing the tumor when possible. High-dose proton pump inhibitors relieve symptoms and prevent ulcers. Surgical resection is preferred for localized disease. In unresectable or metastatic cases, medical therapy includes somatostatin analogs (e.g., octreotide, lanreotide), targeted therapies for neuroendocrine tumors, and peptide receptor radionuclide therapy (PRRT) with Lu-177 DOTATATE. Management often involves multidisciplinary care and, when applicable, screening for MEN1-associated tumors.

Prognosis depends on tumor spread and stage at diagnosis; localized gastrinomas have a better outcome than metastatic disease.