Neuroendocrine Tumor of the Gastrointestinal Tract: Symptoms and Signs

Approved by the Cancer.Net Editorial Board, 07/2022

ON THIS PAGE: You will find out more about the changes and medical problems that can be a sign of a gastrointestinal tract neuroendocrine tumor (GI tract NET). Use the menu to see other pages.

What are the symptoms of a GI tract NET?

A GI tract NET often causes no symptoms in its early stages. This type of tumor is usually found by a surgeon during an unrelated surgery or on imaging (like a CT scan) for another condition.

People with a GI tract NET may experience the following symptoms or signs. The symptoms and signs of carcinoid syndrome and carcinoid crisis, which are conditions that a GI tract NET can cause, are also described. Symptoms are changes that you can feel in your body. Signs are changes in something measured, like taking your blood pressure or doing a lab test. Together, symptoms and signs can help describe a medical problem. However, the cause of a symptom or sign may be a medical condition that is not a GI tract NET.

If you are concerned about any changes you experience, please talk with your doctor. Your doctor will try to understand what is causing your symptom(s). They may do an exam and order tests to understand the cause of the problem, which is called a diagnosis.

GI tract NETs may cause tumor-related symptoms. GI tract NETs are also the type of NET most likely to cause carcinoid syndrome (see below), which has its own set of symptoms.

People with a GI tract NET may experience the following tumor-related symptoms or signs:

  • Abdominal pain caused by blockage of the intestines

  • Diarrhea, especially in people who have carcinoid syndrome, had part of their intestines removed, or had their gallbladder removed.

  • Rash

  • Bright, red blood in the stool or dark, tarry stool. This is a sign of intestinal bleeding.

  • Scale-like skin sores, which can be a sign of pellagra, a severe deficiency of vitamin B3

  • Mental confusion or other problems, another sign of pellagra

  • Constipation

  • Nausea and vomiting

  • Weight loss that cannot be explained

  • Jaundice, which is when the skin and whites of the eyes turn yellow

  • Fatigue

Carcinoid syndrome

Carcinoid syndrome is the classic example of a functional NET and occurs most commonly in people with a small intestine NET. In carcinoid syndrome, the tumor produces hormones, mainly serotonin, that can cause symptoms. Serotonin is often measured in the urine, when it gets converted into 5-hydroxyindoleacetic acid (5-HIAA), and it is measured with a 24-hour urine collection. But 5-HIAA can be also measured in the blood. Not all people with a NET develop carcinoid syndrome.

People with carcinoid syndrome may experience 1 or more of the following symptoms or signs. It is important to note that these symptoms alone are not enough to diagnose carcinoid syndrome. Blood or urine tests to measure for suspected hormones are also needed to make a diagnosis.

  • Facial flushing, which is redness and a warm feeling over the face

  • Sweating

  • Diarrhea

  • Shortness of breath

  • Wheezing or asthma-like symptoms

  • Weakness

  • Fast heartbeat

  • Heart murmur

  • High blood pressure and significant fluctuations in blood pressure

  • Carcinoid heart disease, which is a scarring of the heart valves

Stress, strenuous exercise, and drinking alcohol may make these symptoms worse. Some foods may also trigger the symptoms of carcinoid syndrome, including foods high in:

  • Amines, such as aged cheeses, yeast extracts, tofu, sauerkraut, and smoked fish and meats

  • Serotonin, such as walnuts, pecans, plantains, bananas, and tomatoes

Carcinoid crisis

Carcinoid crisis is a term used when a person with a NET experiences severe, sudden symptoms of carcinoid syndrome. This usually happens due to extreme stress such as surgery. Carcinoid crisis primarily includes serious fluctuations in blood pressure and heart rate. Carcinoid crisis is the most serious and life-threatening complication of carcinoid syndrome. A carcinoid crisis may be prevented and successfully treated with octreotide, which is usually given through a vein before a medical procedure or surgery.

Managing symptoms of carcinoid syndrome

If a GI tract NET is diagnosed, relieving symptoms remains an important part of cancer care and treatment. Managing symptoms may also be called "palliative and supportive care,” which is not the same as hospice care given at the end of life. This type of care focuses on managing symptoms and supporting people who face serious illnesses, such as cancer. You can receive palliative and supportive care at any time during cancer treatment. Learn more in this guide’s section on Coping With Treatment.

Below is information on how some of the symptoms of a GI tract NET can be managed, in addition to treatment with a somatostatin analog like octreotide or lanreotide. Be sure to talk with your health care team about the symptoms you experience, including any new symptoms or a change in symptoms.

  • Facial flushing. Avoid stress. Ask your doctor about specific substances and foods, including alcohol, that can cause facial flushing, so you can avoid them.

  • Wheezing. Ask your doctor about the use of a bronchodilator, a medication that relaxes the muscles in the lungs to make breathing easier.

  • Diarrhea. There can be many causes of diarrhea in people with a NET. If your diarrhea is caused by carcinoid syndrome, somatostatin analogs and telotristat ethyl (Xermelo) may help. If the diarrhea is caused by a problem with the absorption of bile acid, which occurs after removal of the gallbladder, ursodiol (Actigall, URSO 250, URSO Forte) may help. If a lack of pancreatic digestive enzymes has caused the diarrhea, replacement enzymes can help. Ask your doctor for specific recommendations for you.

  • Heart problems. Tell your doctor immediately if you think you may have a problem with your heart. Ask about the use of diuretics. Diuretics are drugs that lower blood pressure by helping the body get rid of water and sodium.

Learn more about managing common cancer symptoms and treatment side effects.

The next section in this guide is Diagnosis. It explains what tests may be needed to learn more about the cause of the symptoms. Use the menu to choose a different section to read in this guide.