9 Types of Neuroendocrine Tumors

Neuroendocrine tumors are a very rare type of cancer that begin in neuroendocrine cells. Only 8,000 adults in the U.S. are diagnosed with neuroendocrine tumors of the gastrointestinal (GI) tract each year, and that’s the most common type of neuroendocrine tumor. For comparison, 30 times that are diagnosed with breast cancer, and 13 times that are diagnosed with colon cancer each year in the U.S. 

Neuroendocrine cells make and release hormones. These hormones travel to other parts of the body and help regulate important functions, like: 

• Digestion

• Blood pressure

• Heart rate

• Bone and muscle growth

Unlike other types of cancer, neuroendocrine tumors can start in many parts of the body. Some people can develop many neuroendocrine tumors, especially if they have a condition called multiple endocrine neoplasia type 1 (MEN1) syndrome. But most people only develop neuroendocrine tumors in one place.

All types of neuroendocrine tumors are similar in how they start: They’re caused by a change (mutation) in a neuroendocrine cell that leads to cancer. But that’s where the similarities end. Other than that, different types of neuroendocrine tumors don't have a lot in common. 

1. Neuroendocrine tumors of the gastrointestinal tract 

Neuroendocrine tumors of the GI tract are the most common type of neuroendocrine tumors. 

Neuroendocrine cells are found throughout the lining of the gut, so neuroendocrine tumors can start anywhere along the GI tract. But the most common places neuroendocrine tumors start are in the:

• Appendix

• Small Intestine

• Rectum

It’s possible to have multiple neuroendocrine tumors throughout the GI tract. But this is uncommon. 

Some types of neuroendocrine tumors of the GI tract can make and release a hormone called serotonin. When this happens, it’s called carcinoid syndrome. 

Symptoms of carcinoid syndrome are:

• Flushing and skin redness

• Sweating

• Diarrhea

• Shortness of breathing or trouble breathing

• Fast heart rate

• High blood pressure

Other types of neuroendocrine tumors can also cause carcinoid syndrome, especially neuroendocrine tumors of the lungs. 

2. Neuroendocrine tumors of the lungs

Neuroendocrine tumors of the lungs are the second most common type of neuroendocrine tumor. They make up about 20% to 30% of neuroendocrine tumors. 

Neuroendocrine tumors usually start in the airways of the lungs (bronchial neuroendocrine tumors). But they can also start in the tissue of the lungs and are called:

• Small cell lung cancer

• Large cell neuroendocrine carcinoma  

Neuroendocrine tumors of the lungs can make and release serotonin, too. But this is uncommon. Less than 1 in 10 people with these types of neuroendocrine tumors develop carcinoid syndrome. People don’t tend to develop carcinoid syndrome unless they have a large tumor.

In very rare cases, these tumors can release other hormones which can trigger hormonal imbalances like acromegaly or Cushing’s syndrome. 

3. Neuroendocrine tumors of the pancreas

Neuroendocrine tumors of the pancreas are the third most common type of neuroendocrine tumors. About 7% of all neuroendocrine tumors start in the pancreas. 

Like the healthy cells that make up the pancreas, neuroendocrine tumors of the pancreas can make different hormones. The symptoms a person may feel depend on the hormone or hormones being made:

• Insulin: High levels of insulin can cause symptoms of low blood sugar (hypoglycemia) like sweating, dizziness, confusion, and weakness. 

• Gastrin: High levels of gastrin increase the amount of acid the stomach makes. This can lead to stomach ulcers. 

• Glucagon: High levels of glucagon lead to high blood sugar, which can cause diarrhea, a rash, and symptoms similar to diabetes.

• Vasoactive intestinal peptide: High levels of vasoactive intestinal peptide can cause watery diarrhea and low potassium levels (hypokalemia).

• Somatostatin: High levels of somatostatin can cause oily diarrhea (steatorrhea), high blood sugar, and gallstones. 

A neuroendocrine tumor of the pancreas can make one or more of these hormones at a time. But some tumors do not make enough hormones to cause any symptoms.

Just over 90% of all neuroendocrine tumors start in either the GI tract, lungs, or pancreas. The remaining 10% start in other parts of the body. These types of tumors are extremely rare. 

4. Pheochromocytomas 

Pheochromocytomas are tumors that start in the adrenal glands. The body has two adrenal glands, which are located above the kidneys. Pheochromocytomas develop in the cells that make up the inner layer of the adrenal glands. 

Pheochromocytomas make hormones called epinephrine and norepinephrine. Surges in these hormones lead to symptoms like:

• Rapid heart rate

• Palpitations

• High blood pressure

• Shakiness

• Sweating 

• Headaches

These surges can also put people at risk for serious health problems, including strokes, heart attacks, and sudden death. 

But pheochromocytomas rarely spread beyond the adrenal glands. So, once they’re diagnosed, they can be treated and even cured with surgery. 

5. Paragangliomas

Paragangliomas also form in clusters of nerve cells (ganglia) that surround major blood vessels, especially in the head and neck. Like pheochromocytomas, they can release epinephrine and norepinephrine. 

They’re very slow growing and are often caught before they have a chance to spread. That means they can often be treated and cured with surgery.

6. Pituitary neuroendocrine tumor

Pituitary neuroendocrine tumors start in the pituitary gland. The pituitary gland is attached to the brain, and it releases several hormones. Pituitary neuroendocrine tumors are not a type of brain cancer because they start in neuroendocrine cells — not the cells that make up parts of the brain.

Pituitary neuroendocrine tumors are also called pituitary adenomas. These types of tumors can release hormones that can lead to conditions like:

• Cushing’s syndrome

• Acromegaly

• Amenorrhea (irregular or lack of menstruation)

• Galactorrhea (breast milk production not related to pregnancy and delivery)

7. Medullary thyroid cancer

The thyroid is an organ in the neck that makes thyroid hormone. Medullary thyroid cancer is a rare type of thyroid cancer that starts in the C-cells of the thyroid. These cells make a hormone called calcitonin.

Medullary thyroid cancer is rare. Only about 1,000 people are diagnosed with this type of thyroid cancer each year. 

8. Neuroendocrine tumors of the reproductive system

Neuroendocrine tumors can develop in both the male and female reproductive systems. They may start in the:

• Testicle

• Prostate

• Ovary

• Cervix

• Uterus (endometrium)

• Vagina

• Vulva

These types of tumors are extremely rare. Only a few dozen people are diagnosed with these types of tumors each year. 

9. Neuroendocrine carcinoma of the skin

Neuroendocrine carcinoma of the skin is a very rare type of skin cancer. It’s also called Merkel cell carcinoma because the cancer begins in the Merkel cells. These cells are found in the top layer of the skin. 

Neuroendocrine carcinoma of the skin usually starts out as a skin lump. Unlike other types of skin cancer, it can grow and spread quickly. 

This type of cancer is very rare. Only about 1,600 people are diagnosed with it each year. Many cases are linked to Merkel cell polyomavirus. This is a silent virus that can trigger cancer similar to how the HPV virus can cause cervical cancer and the hepatitis B virus can cause liver cancer.

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Written by:

Patricia Pinto-Garcia, MD, MPH

Patricia Pinto-Garcia, MD, MPH, is a medical editor at GoodRx. She is a licensed, board-certified pediatrician with more than a decade of experience in academic medicine.

Reviewed by:

Sophie Vergnaud, MD

Sophie Vergnaud, MD, is the Senior Medical Director for GoodRx Health. An experienced and dedicated pulmonologist and hospitalist, she spent a decade practicing and teaching clinical medicine at academic hospitals throughout London before transitioning to a career in health education and health technology.

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