Gastrointestinal Neuroendocrine Tumors (GI NET)

Gastrointestinal neuroendocrine tumors are rare cancerous tumors in neuroendocrine cells in your gastrointestinal (GI) tract. The most common treatment is surgery to remove the tumor.


What are gastrointestinal neuroendocrine tumors (GI NET)?

Gastrointestinal neuroendocrine tumors (GI NET) are rare cancerous tumors in neuroendocrine cells in your gastrointestinal (GI) tract. The most common treatment is surgery to remove tumors.

How does GI NET affect my body?

A gastrointestinal neuroendocrine tumor is one of a group of uncommon tumors (neuroendocrine tumors) that start in specialized cells in your neuroendocrine system. Neuroendocrine cells link your endocrine system (which manages your hormones) and your nervous system. Neuroendocrine cells are scattered throughout your body, including your gastrointestinal tract.

Your gastrointestinal tract is part of your digestive system. Your GI tract is a tube-like pathway your body uses to digest food and liquid and to process waste. GI NETs (once called carcinoid tumors) typically develop in your small intestine and rectum, but may also appear in your stomach, appendix and esophagus. Gastrointestinal endocrine tumors can spread beyond your GI tract to your liver.

Who’s affected by gastrointestinal neuroendocrine tumors?

GI NET affects about 4 in 100,000 people. Each year, about 8,000 adults in the U.S. are diagnosed with gastrointestinal endocrine tumors. The condition typically affects people aged 55 to 65, but it can affect adults of any age. GI NET is more common in white people than in Black people. Women and people assigned female at birth are slightly more likely to develop GI NET than men and people assigned male at birth.


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Symptoms and Causes

What are the symptoms of GI NET?

People may have these tumors without having symptoms. Some people are diagnosed with GI NET because they had an imaging test to diagnose an unrelated condition. When people do have symptoms, the symptoms are similar to symptoms for less serious illnesses. Common GI NET symptoms include:

  • Stomach pain: This could be a sign a GI NET has blocked your intestines.
  • Diarrhea: This symptom often affects people who have carcinoid syndrome or who’ve had their gallbladder or part of their intestines removed.
  • Nausea and vomiting: Persistent nausea and vomiting may be a symptom of serious illness.
  • Unintentional weight loss: Losing weight quickly without dieting or exercising is a common GI NET symptom.
  • Bright red blood in your poop (stool) or poop thats dark-colored and tarry: These symptoms might be signs you have intestinal bleeding.
  • Jaundice: This condition causes your skin and the whites of your eyes to turn yellow.
  • Fatigue: This symptom is more than feeling sleepy. Fatigue means you’re exhausted all the time.

What causes gastrointestinal endocrine tumors?

Medical researchers haven’t identified a specific cause. They’ve found links between GI NETs and hypochlorhydria (low stomach acid). People with certain inherited conditions and syndromes may develop GI NET. Those conditions and syndromes include:

  • Multiple endocrine neoplasia (MEN): There are two types of MEN. One type (MEN1) causes your thyroid, parathyroid or adrenal glands to be overactive or form tumors. Another type (MEN2) affects your pancreas, pituitary or parathyroid to be overactive or form tumors.
  • Von Hippel-Lindau disease: This is a rare condition where benign tumors grow in various parts of your body.
  • Neurofibromatosis type 1: This is a rare condition where tumors grow on your skin and nerves, affecting your eyes and other parts of your body.


Diagnosis and Tests

How do healthcare providers diagnose gastrointestinal neuroendocrine tumors?

  • X-ray: An x-ray is a way to create a picture of the structures inside the body. Sometimes, a GI NET may not show up on an X-ray because of its size or location, so the healthcare provider may recommend other types of scans.
  • Computed tomography (CT) scan: CT scans use a computer and a series of X-rays to produce a three-dimensional view of your organs and bones. CT scans may show the tumor’s size or if it’s spread to your liver or other areas of your body.
  • Magnetic resonance imaging (MRI): This test produces detailed images of your organs and bones using a magnet, radio waves and a computer.
  • Endoscopy: Healthcare providers use an endoscope, a thin, tube-like instrument with a light and lens, to view the lining of your upper digestive system. They insert the endoscope through your mouth or rectum. They may use a colonoscope to view the lower section of your digestive tract.
  • Endoscopic ultrasound (EUS):Providers use an endoscope and high-energy sound waves to obtain pictures of your digestive tract. They insert the endoscope through your mouth or rectum. A probe at the end of the endoscope bounces sound waves off your internal tissues, making echoes that form pictures called sonograms.
  • Positron emission tomography (PET) scan: This test tracks neuroendocrine tumors using a special dye that was specifically designed to detect neuroendocrine tumor cells.
  • Biopsy: Providers remove a small amount of tissue for examination under a microscope.

Are there grades of neuroendocrine tumors?

Yes, healthcare providers use a grading system to categorize the tumor so they can plan treatment. To establish a tumor grade, they examine cancerous cells under a microscope. That view shows them how many cells are dividing and how quickly, and if cells look more like healthy cells than cancerous cells. GI NET grades include:

  • Grade 1 (low-grade tumor): These cells divide at a low rate and are growing slowly.
  • Grade 2 (intermediate-grade tumor): These cells divide at an intermediate rate.
  • Grade 3 (high-grade tumor): These cells divide at a fast rate and, therefore, grow quickly.


Management and Treatment

What are treatments for gastrointestinal endocrine tumors?

There are several ways to treat GI NET. Healthcare providers will recommend treatment based on your cancer’s grade, treatment side effects, your overall health and your personal preferences. Treatments include active surveillance, surgery and medical treatments.

What is active surveillance?

Providers may recommend active surveillance if the tumor is growly very slowly and isn’t likely to spread to other areas of your body. Active surveillance includes:

What surgeries treat GI NET?

Surgery for gastrointestinal endocrine tumors depends on the tumor’s location and if it’s spread to other areas of your body.

Regardless of your specific surgery to treat your GI NET, it’s essential that your surgery team knows you have carcinoid syndrome, a set of symptoms that are signs of neuroendocrine tumors. If you have carcinoid syndrome, surgery may trigger potentially life-threatening complications. When your surgeon knows you have this condition, they’ll use special medication before, during and after your surgery to prevent complications. Common GI NET surgeries include:

  • Partial gastrectomy: This surgery removes part of your stomach.
  • Small intestine resection: This surgery removes the part of your small intestine containing your tumor. Your surgeon may perform an anastomosis (joining the cut ends of your intestine together). They’ll usually remove lymph nodes near your small intestine and examine them under a microscope to see whether they contain cancer.
  • Appendectomy: Surgeons may use an open incision or laparoscopic surgery to remove your appendix.
  • Hemicolectomy: They’ll remove the right or left side of your colon, including nearby blood vessels and lymph nodes.
  • Lower anterior resection: Surgeons remove part of your rectum, leaving your anus intact so you can poop (eliminate stool) normally.
  • Abdominoperineal resection (APR): This surgery removes your anus, rectum and part of your colon. This surgery often includes a colostomy, which is an opening from your colon to your stomach surface that enables you to get rid of your poop (digestive waste).
  • Liver resection: Surgeons remove the GI NET in your liver.

What complications or side effects do these surgeries have?

All of these surgeries may have significant side effects. In some cases, you may need additional help at home as you recover from your surgery. Ask your healthcare provider what you can expect after your specific surgery.

Will GI NET surgery affect my lifestyle?

It may. In most cases, your surgery will involve removing part of your digestive tract. This could affect your lifestyle, from how and what you eat to how you go to the bathroom. Your surgeon will explain exactly how surgery may affect you and what they’ll do to help you manage your digestive tract issues.

What are other treatments for GI NET?

Healthcare providers may combine surgery with some of these treatments:

  • Chemotherapy: Healthcare providers use a range of drugs designed to kill cancer cells.
  • Targeted therapy: Targeted therapy uses drugs or other substances to attack cancer cells without hurting normal cells.
  • Immunotherapy: Immunotherapy harnesses your body’s immune system to kill cancer cells or keep them from growing.
  • Radiation therapy: Radiation therapy uses strong beams of energy to kill cancer cells or keep them from growing.
  • Somatostatin analogs: Somatostatin analogs are synthetic forms of the somatostatin hormone. Your somatostatin hormone stops your body from making too many hormones.

What are these treatments’ side effects or complications?

Each of these treatments affects people in different ways. Ask your healthcare provider to explain each treatment’s benefits and side effects so you understand how each one may affect you. Your healthcare provider will consider your overall health and your personal preferences when recommending treatment.


Can gastrointestinal endocrine tumors be prevented?

Unfortunately, there’s no known way to prevent GI NET. Medical researchers have discovered some links between certain hereditary syndromes and/or medical conditions that may increase your risk of developing neuroendocrine tumors. Talk to your healthcare provider about your medical history and your family’s medical history. They may recommend specific tests to monitor for early signs of GI NET so they can catch and treat tumors early on.

Outlook / Prognosis

What can I expect if I have this condition?

Your prognosis, or expected outcome, may depend on when a tumor was diagnosed and treated. Approximately 97% of people with GI NET who received treatment before the tumor spread were alive five years after diagnosis. That five-year survival rate drops to 95% if the tumor spreads to nearby tissues or lymph nodes. Approximately 67% of people whose GI NET spread outside of their digestive tracts were alive five years after diagnosis.

GI NET can come back. Depending on the tumor’s size, grade and location, you may have regular follow-up tests. For example, your provider may recommend you have annual CT scans for the first three years after treatment and annual physicals every year. Ask your healthcare provider about follow-up visits and tests for your specific situation.

Living With

How do I take care of myself?

You’ll likely need surgery if you have a gastrointestinal neuroendocrine tumor. Surgeons typically use open incisions rather than laparoscopic surgery. That means you may need to stay in the hospital for several days and then recover at home for several weeks.

When should I go to the emergency room?

You may have a regular follow-up schedule so your healthcare provider can check for signs your cancer has come back. Ask your surgeon what post-surgery symptoms may be signs of a serious issue. You should seek immediate medical care if you experience any of the following:

  • Sudden severe shortness of breath.
  • Fever higher than 100.4 degrees Fahrenheit (38.3 degrees Celsius).
  • Pain that gets worse or that you can’t manage with your pain medication.
  • Green, smelly discharge from your surgery site, particularly if the area around your site feels hot to your touch or is dark red.
  • Persistent vomiting or diarrhea.

A note from Cleveland Clinic

Gastrointestinal neuroendocrine tumor (GI NET) may be a life-changing illness. That’s because most people with this condition need surgery that removes part or all of their digestive tracts. Your surgery may change how you eat or go to the bathroom. Your healthcare providers know it’s not always easy to make these changes. If you have concerns, share them with your provider. They’ll understand your situation and help you find solutions.

Medically Reviewed

Last reviewed on 01/10/2023.

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