Neuroendocrine Tumor of the Gastrointestinal Tract: Symptoms and Signs

Approved by the Cancer.Net Editorial Board, 10/2019

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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 x-rays for another condition. People with a GI tract NET may experience the following symptoms or signs. The signs and symptoms of carcinoid syndrome and carcinoid crisis, which are conditions that a GI tract NET can cause, are also described. However, the cause of a symptom may be a different 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 ask how long and how often you’ve been experiencing the symptom(s), in addition to other questions. This is to help figure out the cause of the problem, called a diagnosis.

Symptoms of a GI tract NET

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 disturbances, 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 those with NETs in either the small intestine or lung that have spread to another part of the body. This spread is called metastasis. In carcinoid syndrome, the tumor produces serotonin, which can cause symptoms or signs. Serotonin is most easily and reliably measured in the urine, when it gets converted into 5-hydroxyindoleacetic acid (5-HIAA), and it is measured with a 24-hour collection. Not all people with a GI tract 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

  • Unexplained weight gain

  • 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

Carcinoid syndrome may damage the heart, so reducing serotonin levels is important. Carcinoid syndrome may be prevented and successfully treated with a somatostatin analog, a medication that helps control the production of hormones, like octreotide (Sandostatin) or lanreotide (Somatuline Depot). Sometimes short-acting octreotide given as an injection under the skin or through the veins is used to treat carcinoid syndrome more urgently.

Stress, strenuous exercise, and drinking alcohol may make carcinoid syndrome 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, usually in times of 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 procedures or surgeries.

Managing symptoms of carcinoid syndrome

If a GI tract NET is diagnosed, relieving symptoms remains an important part of cancer care and treatment. This may be called palliative care or supportive care. It is often started soon after diagnosis and continued throughout 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 NETs. If your diarrhea is caused by carcinoid syndrome, somatostatin analogs and telotristat ethyl (Xermelo) can help. If the diarrhea is caused by bile acid malabsorption, which occurs after removal of the gallbladder, ursodiol (Actigall, URSO 250, URSO Forte) can help. If a lack of pancreatic digestive enzymes has caused the diarrhea, replacement enzymes can help. Ask your doctor for specific recommendations.

  • Heart problems. Tell your doctor immediately if you think you may have a problem with your heart and 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.