Types of Neuroendocrine Tumors and Their Symptoms

Reviewed by Brunilda Nazario, MD on May 01, 2020

When you have neuroendocrine tumors (NETs), you can get a lot of symptoms, from shortness of breath to headaches to cramps in your belly. Why the variety? It's all about location and the type of hormone they make. Your tumors can show up in lots of places, and where they grow and what they release makes a big difference in how you feel.

The trouble with finding NETs is they often don't cause symptoms at first. Some of the tumors grow very slowly, so they may not cause problems for a long time.

Even if you do feel like something's not right, you might not connect it with NETs. Often, the symptoms are things that could have many causes, like digestive problems, headaches, or coughing.

Types of NETs

These tumors affect a type of cell called a neuroendocrine cell. NETs can form anywhere in your body where you have those, and they're often named based on where they grow.

Carcinoid tumors are a type of NET that grows in the:

  • Digestive system: stomach, small intestine, colon, or rectum
  • Lungs
  • Pancreas
  • Ovaries or testicles (rarely)


You may hear your doctor refer to carcinoid tumors as "well-differentiated." That's just a technical way of saying they look similar to normal cells under a microscope. They often grow slowly.

Pancreatic NETs start in the islet cells of the pancreas, a gland in your belly. Your doctor may say your tumors are "functional" or "nonfunctional."

Functional tumors make their own hormones that cause symptoms. Hormones are chemicals that control different actions in your body, like your digestion, blood sugar levels, and heart function.

Nonfunctional tumors don't make any hormones, but they can grow and spread from their original spot to other places in your body.

There are a few kinds of functional pancreatic NETs, which are named after the hormone they release. For example, insulinomas make too much insulin, which lowers levels of your blood sugar. Glucagonomas make too much glucagon, which raises blood sugar and can cause redness or diarrhea. Gastrinomas make gastrin, which helps digest food -- but too much can cause ulcers. Some pancreatic NETs are cancer and others are not.


Medullary carcinoma starts in thyroid gland cells that make calcitonin, a hormone that controls calcium levels in your body. This type of NET often runs in families, and it can spread quickly.

Pheochromocytoma is a rare tumor that forms in the adrenal glands, which sit above your kidneys. It makes the hormones adrenaline and noradrenaline, which control heart rate, blood pressure, and blood sugar. Most pheochromocytomas are not cancer. But the tumor can release hormones that cause heart problems such as a heart attack or stroke.

Merkel cell carcinoma is a rare type of skin cancer. It often starts in parts of the skin that often get a lot of sunlight, such as your head, neck, arms, and legs. It's more likely to spread than other types of skin cancer.

Common NET Symptoms

The symptoms you have with a neuroendocrine tumor depend on where the disease is, whether it makes hormones, and if so, which ones.

A carcinoid tumor in the digestive system will cause symptoms like:

  • Diarrhea and cramps
  • Fatigue
  • Nausea and vomiting
  • Weight loss


When a cancerous NET is in the lung, you might have:

  • A cough
  • Shortness of breath
  • Whistling when you breathe, called wheezing
  • Chest pain

A pancreatic NET that makes hormones can cause symptoms like:

  • Dizziness, weakness, and fast heartbeat
  • Headaches, a frequent need to pee, hunger, thirst, and weight loss
  • Heartburn, pain in your belly, and diarrhea

Even NETs that don't make hormones can cause symptoms by blocking the organ where they grow. You might get a lump or have problems like:

  • Diarrhea
  • Heartburn
  • Pain

Take Action

If you've had symptoms like these, see a doctor who's experienced in treating NETs. These tumors are rare and can be complicated to treat.  

WebMD Medical Reference



American Cancer Society: "Signs and symptoms of gastrointestinal carcinoid tumors," "Signs and symptoms of lung carcinoid tumors,"  "What is a gastrointestinal carcinoid tumor?" "What is Merkel cell carcinoma?"

Merck Manuals: "Carcinoid Tumors and Carcinoid Syndrome."

Emily Chan, MD, PhD, associate professor of medicine and medical oncologist, Vanderbilt-Ingram Cancer Center.

Columbia University Department of Surgery: "Pheochromocytoma."

National Cancer Institute: "Merkel Cell Carcinoma Treatment (PDQ)," "Pancreatic Neuroendocrine Tumors (Islet Cell Tumors) Treatment (PDQ)," "Thyroid Cancer Treatment - for health professionals (PDQ)."

Thomas O'Dorisio, MD, professor of medicine; director of neuroendocrine tumor clinics, University of Iowa.

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