What Are Neuroendocrine Tumors (NETs)?

Medically Reviewed by Murtaza Cassoobhoy, MD on May 23, 2023
Written by Stephanie Watson
9 min read

When you first hear that you've got a neuroendocrine tumor, you'll have lots of questions about what it is and how it will affect you. There are quite a few types of this disease, and it can show up in many places in your body.

Your symptoms may depend on where your tumor is growing and what kind it is. Learn as much as you can about your own type of NET, so you can be a confident partner with your doctor when you make decisions on a treatment plan.

While all this is going on, don't neglect your emotional needs. Your doctor can tell you how to find a support group where you can talk to others who are going through the same things you are. And feel free to open up to your friends and family about how you're doing. They know you best and can be a huge source of support.

The first thing you want to find out about your condition is where your tumor is located. NETs grow in cells that make hormones -- chemicals that help control different actions in your body, like hair growth, your sex drive, and even your mood. A neuroendocrine tumor can grow in spots like your pancreas, a gland in your belly. It can also happen in your stomach, intestines, or lungs.

Some NETs are cancer, which means they can become malignant and spread to other parts of your body. Many of these tumors also make hormones of their own, which can give you certain symptoms. Other kinds of neuroendocrine tumors are benign, which means they don't move from their original spot.

Most neuroendocrine tumors grow slowly -- over years, not months -- compared with other types of tumors. Often, doctors can remove or shrink them with different treatments. Other therapies can make your symptoms better.

There are many types of NETs. They're usually named after the type of cell where they grow, or the hormone they make.

Carcinoid tumors can form in many areas of your body, but they're most common in the cells of the digestive system -- the stomach, small intestines, appendix, and rectum. They can also form in the lungs or a small organ behind the breast bone called the thymus. More rarely, they grow in the pancreas, kidneys, ovaries, or testicles.

These tumors can release different types of hormones, which can affect how you feel. Doctors call these groups of symptoms carcinoid syndrome.

Pancreatic NETs grow in your pancreas. There are a few kinds of them:

Insulinomas are the most common type. Their cells make insulin, the hormone that controls blood sugar levels. Most of the time, they're not cancerous.

Glucagonomas make glucagon, a hormone that raises your blood sugar level. About half of them are cancerous, and they often spread to other parts of your body.

Gastrinomas make the hormone gastrin, which helps you digest food. These tumors can happen if you have a rare disorder called Zollinger-Ellison syndrome. About half of these gastrinomas are cancerous, and they often spread easily in the body.

Somatostatinomas make too much of a chemical called somatostatin that affects how your body makes other hormones.

VIPomas make a hormone that triggers the release of other hormones, called vasoactive intestinal peptides (VIP). Most VIPomas are cancerous.

Some other types of NETs include:

Medullary carcinoma. It shows up in your thyroid gland, an organ that's on the base of your neck. This tumor grows in cells that make a hormone that affects the levels of calcium in your body.

Pheochromocytoma. This grows in cells of your adrenal glands, which sit above your kidneys. It makes the hormones adrenaline and noradrenaline, which can increase your heart rate and blood pressure. Usually these tumors are not cancerous.

Most of the time, doctors don't know what causes NETs. But you're more likely to get them if you have certain diseases that run in your family, such as:

Multiple endocrine neoplasia type 1. This causes tumors to grow in the pancreas and other organs.

Neurofibromatosis type 1. This can cause tumors in your adrenal glands.

Von Hippel-Lindau syndrome. It makes tumors and fluid-filled sacs form in many parts of your body.

 

How a neuroendocrine tumor makes you feel depends on the type you have and where it is in your body.

With a pancreatic NET, you might have:

  • Blurred or double vision
  • Confusion
  • Diarrhea
  • Dizziness
  • A fast heartbeat
  • Headache
  • Hunger that's stronger than usual
  • Rash
  • Shakiness
  • Stomach pain
  • Sweating
  • Weakness
  • Weight loss without trying

Carcinoid tumors can cause:

  • Diarrhea
  • Red, warm, itchy skin, often on your face and neck
  • Coughing
  • Pain in your chest
  • Stomach pain
  • Feeling tired or sick
  • Trouble breathing
  • Weight gain or loss without trying

Other types of NETs can cause:

  • Appetite loss
  • Bleeding
  • Coughing
  • Diarrhea
  • Fever
  • Headache
  • A hoarse voice
  • A fast heart rate
  • Nausea or vomiting
  • Night sweats
  • Pain
  • Rash
  • Sweating
  • Weight gain or loss without trying
  • Yellowish skin or eyes

When you see your doctor, they'll give you a physical exam, and they'll want to hear about how you're feeling. They might ask you questions like:

  • How long have you been feeling this way?
  • Do you have any pain? Where?
  • How is your appetite?
  • Have you gained or lost any weight?
  • Do you feel weak or more tired than usual?
  • Do you have any skin rashes?
  • Do you have any medical conditions?
  • Are there any illnesses that run in your family?

Your doctor can use a few different tests to check for a tumor in your body. You might get:

Blood and urine tests. They check the levels of hormones in your body to see if they're too high or too low.

CT scan. It's a powerful X-ray that makes detailed pictures inside your body.

MRI. It uses powerful magnets and radio waves to make pictures of your organs.

Octreotide scan. In a hospital, you'll get a shot of a small amount of a radioactive liquid through an IV. Then, you'll lie down in a scanner that can make images of your insides. The liquid has a drug called octreotide that will stick to cells on the surface of most NETs. The radiation in the fluid helps doctors see those cells on the picture from the scanner. You'll get two scans over 2 days, but you won't have to spend the night in the hospital. Each scan can take up to 3 hours, but it won't hurt.

X-ray. It uses radiation in low doses to show the inside of your body.

Biopsy. Your doctor will take a small piece of tissue from your body and look at it under a microscope to check for tumor cells. They may use a CT scan to help them find the right area. Or they may use a thin, flexible tube with a small camera, called an endoscope, to look at the lining of your digestive tract. You might be asleep or awake during the procedure, but you'll get medicine to make you more comfortable.

Molecular testing. Your doctor checks the sample of the tumor from the biopsy for certain genes, proteins, and other substances. The results help them decide what kind of treatment you need.

  • What type of NET do I have, and where is it? Is it cancerous?
  • What does this mean for me?
  • Have you treated people with this kind of NET before?
  • Is surgery an option for me?
  • What other treatments do you recommend?
  • How will they make me feel?
  • How will we know if it's working?
  • What changes should I expect in my daily life?
  • Will my children get a NET, too?

Doctors can treat NETs with surgery, radiation, chemotherapy, and drugs. The treatment you get will depend on:

  • What kind of tumor you have and how many there are
  • Whether it's cancerous
  • If it has spread to other parts of your body

Surgery. It's one of the most common treatments for many NETs. It can completely remove some tumors, especially those that aren't cancer and haven't spread.

A surgeon might be able to take out just the tumor. Or they may remove part or all of the organs that have a NET, like the pancreas, stomach, or liver.

Doctors can also use other kinds of surgery for people who can't have a traditional operation or who have many, small tumors.

In one type, called radiofrequency ablation, your doctor will put a probe into the tumor that gives off high-energy radio waves, which kills cancer cells in a certain area.

Another type, called cryosurgery, sends extreme cold directly to a tumor with a thin, hollow tube. For these operations, your doctor might use MRI scans or ultrasounds to guide where the probe should go.

Hormone therapy. This is a common treatment for carcinoid NETs. It uses a man-made version of the hormone somatostatin. These drugs keep the tumor from making hormones that can cause diarrhea and other carcinoid syndrome symptoms. They might also shrink the tumor.

Radiation. This method uses high-energy X-rays to kill cancer cells. You might get this treatment if your tumor has spread or if it's in a place that doctors can't reach with surgery.

Most of the time, you'll get this treatment from a machine outside your body. In some cases, your doctor can place radiation implants near tumors inside your body.

Chemotherapy. It uses drugs to kill cancer cells or to stop them from spreading. You take them by mouth, or a doctor injects them into one of your veins. You might take a single medicine or a mix of different ones for a few weeks.

They can cause side effects -- such as fatigue, nausea, vomiting, and hair loss -- but they stop after your treatment is over. Chemo drugs affect everyone differently. Your doctor can tell you what you can do to feel better during treatment.

Embolization therapy. This can treat NETs that spread to your liver that doctors can't remove with surgery. The goal is to block the blood flow that helps them thrive.

In a hospital, your doctor will put a thin, flexible tube called a catheter into the artery that leads to the liver. Then, they'll inject a substance to plug up the artery. You might also get chemotherapy or radiation during the procedure.

Targeted therapy. It uses drugs that attack certain genes or proteins on tumor cells to kill cancer. This treatment limits damage to the healthy cells in your body, which can happen with radiation or chemotherapy.

Immunotherapy. Immunotherapy is a type of cancer treatment that helps the body’s immune system fight cancer. Studies are currently underway to determine the role immunotherapy can play in treating NETs. 

Your doctor will decide which drug is best for you by testing cells from your tumor first.

You might also take other medicines to keep NETs from growing, including hormones, and drugs to slow your heart rate and reduce stomach acid.

Scientists also are looking for new ways to treat NETs in studies called clinical trials. They test new drugs to see if they're safe and if they work. It can be a way for you to try new medicine that isn't available to everyone. Talk to your doctor about whether it's a good idea for you to join one.

Along with following your treatment, you can try other things to ease your symptoms. Talk to your doctor about what's bothering you and ask them what you can do to feel better.

NETs can make it hard to stay at a healthy weight, so focus on eating the right types of foods to get enough nutrition.

  • Get extra protein from fish, eggs, cheese, and beans.
  • If you feel sick to your stomach, try eating smaller meals more often, instead of three big ones. Ginger ale might help calm your stomach.
  • Avoid high-fat foods, sweets, and sugary drinks.

You might want to try acupuncture, massage, or yoga to help you relax and manage your symptoms while you're getting treatment. Check with your doctor before you start any new activities, though.

Get the advice of your family and friends, and ask them to pitch in when you need some extra help.

How a NET affects you depends on the type of tumor you have, whether it's cancerous, and how much it has spread. But with the right treatment, doctors might be able to shrink the tumors or get rid of them completely.

For information on NETs and support groups, contact the NET Patient Foundation or the Carcinoid Cancer Foundation.