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Gastrinoma

What Is It, Symptoms, Diagnosis, Treatment, and More

Author: Jennifer Cheung, RN, BS

Editors: Antonella Melani, MD, Lisa Miklush, PhD, RN, CNS

Illustrator: Jillian Dunbar

What is gastrinoma?

Gastrinoma is a neuroendocrine tumor (NET) that can originate from G cells in the pancreas, stomach or small intestine. G cells produce the hormone gastrin, which in turn stimulates the secretion of gastric acid in the stomach. Since gastrinomas are made up of G cells, these tumors continuously overproduce and release the hormone gastrin, which in turn stimulate the parietal cells in the stomach to secrete large amounts of gastric acid. Ultimately, the excess gastric acid can lead to erosion or ulcers in the mucosa of the stomach or small intestine. 

Gastrinomas are rare, with an incidence of 0.5 to 3 per million per year. Generally, gastrinomas tend to be small tumors, and can either be solitary or develop in clusters. Gastrinomas can occur sporadically or can be associated with multiple endocrine neoplasia type 1 (also known as MEN-1 or Wermer Syndrome). MEN-1 is an autosomal dominant syndrome that causes primary tumors in endocrine glands such as the parathyroid, pituitary, and pancreas. 

Is gastrinoma cancerous?

Gastrinomas can be benign, which means that they don’t invade nearby tissues, or malignant, meaning that they can invade nearby tissues such as the liver. Malignant gastrinomas can even spread through the lymph to distant tissues. Unfortunately, most gastrinomas are malignant. Gastrinomas associated with MEN-1 tend to be more aggressive.

What are the signs and symptoms of gastrinoma?

Gastrinoma can be asymptomatic or present with signs and symptoms that result from the large amounts of acid in the small intestines. For instance, the signs and symptoms of gastrinoma often include abdominal pain, nausea, vomiting, weight loss, diarrhea, steatorrhea, hypokalemia, gastroesophageal reflux, peptic ulcers, and gastrointestinal bleeding. 

Gastrinoma can lead to a rare condition known as Zollinger-Ellison syndrome, which is characterized by severe, recurrent, and multiple peptic ulcers in part of the small intestine, such as the duodenum and jejunum. 

How is gastrinoma diagnosed?

Diagnosis of gastrinoma can involve laboratory tests, imaging studies, and tissue biopsy. Laboratory tests include fasting serum gastrin levels, where highly increased levels indicate the presence of a gastrinoma. This can be followed by a secretin stimulation test to confirm high serum gastrin levels. 

Since gastrinomas are generally very small in size, a combination of various imaging tests are needed to find their location and assess for metastasis. These include endoscopic ultrasound or duodenal endoscopy. For Zollinger-Ellison syndrome, further specialized scans may be necessary, such as somatostatin receptor scintigraphy, computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) scans.

Finally, diagnosis can be confirmed through biopsy to screen for malignancy and verify evidence of G cell proliferation.

How do you treat gastrinoma?

Treatment depends on location, severity of symptoms or ulceration, and malignancy of the tumor. First-line treatment involves surgical removal of the tumors and, if possible, any spread to nearby tissues or lymph nodes. The vast majority are located in the gastric triangle, a region in the abdomen between the cystic and common bile ducts, the second and third parts of the duodenum, and the neck and body of the pancreas. 

If surgical removal is not possible, individuals can get medical treatment to control their symptoms. This involves high doses of medications that decrease their gastric acid production, such as proton pump inhibitors and H₂ receptor blockers.

What are the most important facts to know about gastrinoma?

Gastrinomas are rare, usually small tumors that can originate from G cells in the pancreas, stomach or small intestine. Most gastrinomas are malignant. Gastrinomas can be solitary or develop in clusters, and can occur sporadically or be associated with multiple endocrine neoplasia type 1 (MEN-1). The G cells in gastrinomas produce excessive amounts of gastrin, which can be asymptomatic or lead to abdominal pain, nausea, vomiting, diarrhea, gastroesophageal reflux, gastrointestinal bleeding, and peptic ulcers. Gastrinoma can lead to a rare condition known as Zollinger-Ellison syndrome, with severe, recurrent, and multiple peptic ulcers. Diagnosis of gastrinoma can involve laboratory tests: for instance, fasting serum gastrin test and a secretin stimulation test, imaging studies to identify tumor location, and tissue biopsy to screen for malignancy. Treatment can involve surgery to remove the tumors, as well as medications such as proton pump inhibitors and H₂ receptor blockers to decrease the gastric acid secretion, thereby helping control the presence of symptoms. 

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