Neuroendocrine & Carcinoid Tumors

What are Neuroendocrine & Carcinoid Tumors (NETs)?

NETs are slow growing tumors that begin in neuroendocrine cells. These cells have two interesting qualities. They have nerve-cell traits and they create hormones. NETs tend to develop over many years and may be hard to diagnose.

Not all NETs are cancers, but they’re all named by where they begin (like “GI-NET” or “adrenal-NET). NETS may form in the lungs, digestive system, endocrine organs (the thyroid, adrenal gland, pituitary gland, thymus), or on the skin. NETs that are cancerous can spread to other parts of the body. Some can be very aggressive.

Types of NETs

The most common NETs are:

  • Carcinoid Tumors: begin in the gastrointestinal (GI) tract, lungs, appendix, thymus, lymph nodes, brain, bone, gonads (ovaries and testes) or skin.
  • Pancreatic Neuroendocrine Tumors: include nonfunctional tumors, insulinomas, glucagonomas, gastrinomas, VIPomas, somatostatinomas, GHRHomas, and others.
  • Pheochromocytoma: a rare NET tumor that can develop in the adrenal gland or other parts of the body. They produce too much of the “fight-or-flight” hormones (like adrenaline), causing high blood pressure.

Risk Factors, Signs & Symptoms


The risks that cause NETs are unknown. Some of the risks may be:

  • Age: Most people are diagnosed over age 60.
  • Race and sex: Women and African Americans are diagnosed more often.
  • Smoking
  • Diet: a high fat, high sugar diet adds to risk.

Signs & Symptoms

Symptoms are caused by the location of the tumor and if the tumor secretes hormones. Tumors are either “functional” or “non-functional”:

    Functional Tumors

    Functional Tumors: when NETs produce abnormal hormones, peptides and proteins, so the body reacts badly. This may be the case with mid-gut and foregut NETs.

    Signs of carcinoid syndrome:

    • Flushed skin (the skin turns red and hot in flashes. Purplish veins show on the face). 
    • Diarrhea
    • Abdominal pain
    • Wheezing
    • Changes in blood pressure
    • Low or high blood sugar

    Later stage functional NETs can also cause: Insulinoma syndrome, Zollinger Ellison syndrome, and VIPoma syndrome.

    Non-Functional Tumors

    Non-Functional Tumors: when NETs don’t produce anything, but the mass can cause problems. In the gut or bowel, NETs can cause an obstruction. Nearer to or in the lung, carcinoid tumors can cause breathing trouble, chest pain and coughing. Other symptoms include:

    • Nausea and vomiting
    • Inability to pass stool (bowel obstruction)
    • Pain
    • Rectal bleeding
    • Sweating, nausea

    Diagnosis & Staging


    Sometimes NETs go un-diagnosed for many years before they’re found. The following tests are used to make a clear diagnosis:

    • Blood/urine tests – to check for abnormal levels of hormones, tumor markers, or genetic traits.
    • Imaging Tests – to look for tumors and measure their size. Some are used to monitor how well treatment works.
      • Computed tomography (CT or CAT) scan with dye
      • Magnetic resonance imaging (MRI) with dye
      • Positron emission tomography (PET) or PET-CT scan
    • Biopsy – a small sample of tissue is removed so a Pathologist can see if and what cancer cells are present. Molecular testing may be done to find specific genes, proteins and other factors.


    Staging defines the tumor’s size, location, stage, grade, and defining characteristics. This information is used to direct your treatment.

    NETs may be local (in one spot), regional (in an area), or metastatic (spread through the body):

    • Low grade: well-defined and local; often treated with surgery.
    • High grade: more aggressive and has spread; treated with more than surgery. 

    There is a formal staging system for carcinoid tumors based on where tumors are found:

    • Stomach
    • Duodenum
    • Ampulla
    • Jejunum
    • Ileum
    • Colon/rectum
    • Pancreas
    • Appendix

    Treatment & Side Effect Management

    Your treatment plan is based on your diagnosis, your general health, symptoms, and practical matters. Your doctor will consider whether or not the tumor(s) can be stopped.

    Often, a few options starting with surgery or ablation therapy are considered for treatment. Hormone therapy, radiation therapy, chemotherapy, immunotherapy or targeted therapies are some of the non-surgical options.

    With treatment, people with NETs can often live long, productive lives.

    Learn More About Treating NETs

    Surgery is done to remove all tumors and nearby lymph nodes. If surgery is not enough or not possible, there are other options. If the cancer has spread to other organs, surgery can be done to prevent symptoms, like bowel obstruction.

    These treatments use thermal heat, cold, or radiation to destroy tumor tissue or block the blood supply to a tumor. They can decrease the tumor’s size, reduce symptoms, and/or slow the growth of a tumor.

    The hormone somatostatin is used to control carcinoid syndrome. Somatostatin regulates the endocrine system and can slow the release of other hormones. It can stop symptoms like flushing, diarrhea, and wheezing.

    High energy x-rays are used to damage the DNA of cancer cells in NETs. Radiation treatment is used to relieve pain from metastases in bones or other parts of the body.

    Chemotherapy drugs travel through the blood to kill cancer cells anywhere in the body. Generally, chemotherapy is only used for NETs that have or will spread to other organs; cause severe symptoms; or don’t respond to other treatments.

    If there are liver metastases, this is a way to cut the tumor’s blood supply and bring high doses of chemotherapy directly to the liver through a catheter.

    This treatment, for people with advanced NETs, targets a specific gene, protein, pathway or other factor found in the cancer cell. There are many types, such as: VEGF Inhibitors that can stop the way tumors grow; or mTOR Inhibitors that can activate cell death. Some targeted therapies are only available through a clinical trial.

    These treatments, like Interferons, are designed to boost your body’s immune-response. These drugs can help the body find and attack NET cells. Some immunotherapies are only available through a clinical trial.

    Clinical trials are studies to find new treatments. Ask your doctor if they would recommend a clinical trial for your treatment. There are many clinical trials studying new ways to treat NETs.

    Treatments to Manage Carcinoid and Other Syndromes

    Treatments to manage symptoms from carcinoid syndrome:

    • Somatostatin analogues (SSAs): to prevent, control, or reduce hormone-related symptoms like skin flushing and diarrhea.
    • Telotristat (Xermelo®): for diarrhea not controlled by an SSA alone
    • Cyproheptadin: to relieve allergy symptoms
    • H1 antagonists: to relieve allergy symptoms
    • Interferons (a type of immunotherapy): to stop or slow tumor growth
    • Hepatic artery embolization (sometimes with chemotherapy): to remove tumors
    • Radiofrequency ablation or electroporation: to remove tumors

    Treatments to manage Zollinger-Ellison Syndrome:

    • Proton Pump Inhibitors (PPIs) to control gastric acid from GI-Nets
    • Diazoxide, to reduce the effects of insulin secretion

    Side Effects & Recovery from NET Treatments

    Ask your health care team, upfront, about side effects. You can work together to limit problems. It will be important for you to speak-up and ask questions along the way.

    Nutrition counseling, relaxation techniques, emotional support and physical therapy are all things you can do to help speed your recovery and improve your overall well-being.

    Surgical side effects: Since surgery can lead to bleeding or infection during recovery, make sure to take the time you need to recover well. Ask about steps to avoid infection.

    Non-surgical side effects: Drug therapies can cause fatigue, upset stomach, nausea, low blood counts, diarrhea, hair loss, and skin reactions. There are medications for many of these issues. They tend to go away after the treatment period ends.

    Damage to the heart: Long-term use of serotonin to treat carcinoid syndrome can cause heart problems. You may feel tired, short of breath and have swollen ankles. You should see a Cardiologist for your care. Patients with serious carcinoid heart disease may use somatostatin analogues (such as octreotide) or need heart surgery (valve replacement).

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