Causes of Neuroendocrine Tumors

Medically Reviewed by Jennifer Robinson, MD on June 24, 2024
4 min read

The plain truth is, that experts don't know exactly what causes neuroendocrine tumors (NETs). But a bunch of things can make you more likely to get them. Doctors call these "risk factors." They might be certain diseases or other situations you don't have any control over, like how old you are.

Keep in mind, that just because you have a higher risk for NETs doesn't mean you'll get a tumor. But talk to your doctor if you find yourself saying "yes" to some items on this checklist.

Some diseases caused by genes that are passed to you through your family can raise your chances of getting a tumor. If you have a parent with one of these diseases, you are slightly more likely to get some types of NETs:

Multiple endocrine neoplasia type 1 (MEN1). It's a disease that causes tumors to form in the cells that make hormones -- chemicals that affect actions in your body like hair growth, sex drive, and mood.

The disease starts from a change to the MEN1 gene. You may hear your doctor call this a "genetic mutation."

If you have the condition, you may be more likely to get cancers of the parathyroid gland, pituitary gland, and pancreas, including pancreatic NETs. One out of every 10 people with MEN1 will get a carcinoid tumor.

Most MEN1 tumors are not cancer. But they can release hormones that affect the way your body works.

Multiple endocrine neoplasia type 2 (MEN2). It can raise your risk for tumors in the thyroid, adrenal, and parathyroid glands. There are 2 types of MEN2.

It's caused by a change to the RET gene.

If you have MEN2, you're more likely to get neuroendocrine tumors such as pheochromocytoma, medullary thyroid cancer, and parathyroid tumors.

Neurofibromatosis type 1 (NF1). It causes tumors to form along your nerves and skin. If you have it, you may also get colored patches on your skin, called café au lait spots.

Changes in the NF1 gene cause this disease. The gene normally makes a protein called neurofibromin, which makes cells grow in an orderly way. When the NF1 gene changes, your cells may grow out of control and form cancer.

If you have NF1 you're more likely to get NETs such as carcinoid tumors and pheochromocytoma.

Von Hippel-Lindau syndrome (VHL). It leads to the growth of abnormal blood vessels, tumors, and fluid-filled sacs called cysts around different parts of your body.

The tumors often affect the eyes, brain, pancreas, adrenal glands, kidney, and spine. Most of them aren't cancer, but some can grow and spread. If you have VHL, you're also more likely to get pheochromocytoma.

Tuberous sclerosis complex (TSC). It makes tumors grow in the brain, kidneys, heart, lungs, skin, and eyes. They're not cancerous, but they can cause seizures and learning problems.

TSC is caused by changes to two genes: TSC1 and TSC2. If you have this condition, you're more likely to get pancreatic NETs or carcinoid tumors.

If one of these diseases runs in your family, your doctor will test you for the gene that causes it. They may check for tumors, so you can get treated before they can grow and cause problems.

Some types of NETs affect people of certain ages.

  • Carcinoid tumors are often diagnosed in your 50s and 60s.
  • Pheochromocytoma usually starts if you're 40 to 60.
  • Merkel cell cancer tends to happen when you're over 70.

Gender affects your risk for certain NETs. Men are more likely to get pheochromocytoma and Merkel cell cancers. Women are at slightly higher risk for most carcinoid tumors.

African Americans are more likely than whites to get carcinoid tumors of the stomach, intestines, and other parts of the GI tract.

Your immune system is your body's defense against germs. Anything that weakens it, such as HIV or an organ transplant, can raise your risk for NETs.

If you spend a lot of time outdoors over the years, it can increase your risk for a NET called Merkel cell carcinoma. The sun gives off UV rays, which damage DNA in your skin. That can cause cells to grow out of control and form cancer.

Diseases that affect the way your stomach makes acid can add to your risk for carcinoid tumors. These include:

  • Chronic atrophic gastritis
  • Pernicious anemia
  • Zollinger-Ellison syndrome

If you've had diabetes for many years, you may be slightly more likely to get NETs of the stomach and intestines.

You've already heard how bad it is for your health. It's not just lung cancer you have to worry about, though. Some studies suggest that smoking increases the risk for carcinoid tumors of the small intestine.