How Are Neuroendocrine Tumors Different From Other Types of Tumors?

There are many types of tumors. And, let’s face it, no one wants to get the news they have one. So we’re here to help you understand the details so you can confidently approach the next steps. 

Neuroendocrine tumors (NETs) are a rare type of tumor. Only about 12,000 people in the U.S. are diagnosed with NETs per year. There are many different types of NETs, and they can occur anywhere in the body. NETs equally affect men and women. Most NETs grow slowly and are very treatable. 

In this article, we discuss the causes, symptoms, diagnosis, and treatment of NETs.

What are neuroendocrine cells?

To understand NETs, you first need to understand a bit about the cells they come from — neuroendocrine cells. “Neuro” means nerves, and “endocrine” means hormones. So neuroendocrine cells are special cells that respond to signals from nerves by releasing hormones.  

Neuroendocrine cells are found all over the body. Locations include the:

• Stomach and bowels (gastrointestinal tract)

• Lungs

• Pancreas

• Pituitary gland (brain)

• Adrenal glands 

• Thyroid and parathyroid glands in the neck

• Kidneys and bladder

• Genital organs (like the ovaries and prostate)

What causes neuroendocrine tumors?

NETs happen when a neuroendocrine cell becomes cancerous. Cancerous cells result from changes (mutations) in DNA that cause them to reproduce rapidly. The more copies a cancerous cell makes of itself, the bigger the tumor. 

Some NETs are hereditary — meaning they’re related to genetic conditions that cause tumors. Multiple endocrine neoplasia type 1 is an example. But most NETs are sporadic — meaning they happen out of nowhere.

How are neuroendocrine tumors different from other tumors?

NETs differ from other tumors in two ways:

1. Location: Neuroendocrine cells are all over the body, and so are NETs. Other tumors start in specific organs. For example, breast cancer starts in the breast. But NETs can start anywhere. The most common locations include the gastrointestinal tract (65%) and lungs (25%).

2. Release of hormones: Some NETs are “functional” — meaning they release more hormones than they should. Too much of any hormone leads to specific symptoms that other tumors don’t have. 

What are the symptoms of a neuroendocrine tumor?

Since there are so many different kinds of NETs, symptoms vary. Every person has their own unique combination of symptoms, and some people may not have symptoms at all. 

Symptoms fall into three main categories.

1. General cancer symptoms

• Weight loss

• Lack of appetite

• Fatigue

2. Symptoms related to tumor location

• Pain

• Lump or mass-like growth

• Shortness of breath, cough, or coughing up blood (tumors in the lung)

• Diarrhea, constipation, or bloody stools (tumors in the gastrointestinal tract)

3. Symptoms related to the release of hormones

• Abdominal pain, stomach ulcers, and diarrhea — when NETs release too much stomach acid 

• Low blood sugar — when NETs release too much insulin

• Flushing of the face, wheezing, rapid heartbeat, and diarrhea (carcinoid syndrome)

How do you diagnose a neuroendocrine tumor?

NETs can be harder to diagnose than other types of tumors since there are so many different kinds of them. NETs that release hormones tend to be diagnosed earlier because the symptoms of too much hormone prompt people to seek medical care sooner. 

To diagnose a NET, your healthcare provider might order any of these tests:

• CT or MRI imaging

• Endoscopy, which involves inserting a camera into the stomach or rectum to examine the inside of the stomach or bowels

• Special imaging, which involves injecting a radioactive substance into a vein to locate tumor cells (like octreotide scans)

• Blood or urine tests to check hormone levels (tumor markers)

A primary care provider or emergency room doctor may diagnose NETs. If testing confirms a cancer diagnosis, an oncologist (cancer specialist) will take the lead when it comes to treatment.

How do you treat a neuroendocrine tumor?

Most NETs are very treatable. Treatment depends on a couple of different factors:

• Type of neuroendocrine cell causing the NET

• Location of the NET

• Any metastasis (spread) of the NET and how quickly the NET is growing or spreading

Surgery is often the treatment for NETs that haven’t spread yet. Medications are preferred for the 12% to 22% of NETs that have metastasized at the time of diagnosis. Recommendations for medication usually depend on the type of NET. Researchers are working hard to develop new treatments. 

A solid support system and tools to help cope with a cancer diagnosis and treatment are important, too.

Why trust our experts?

Written by:

Samantha C. Shapiro, MD

Samantha Shapiro, MD, is a board-certified rheumatologist and internist with expertise in autoimmune and inflammatory conditions. She founded the division of rheumatology at Dell Medical School at The University of Texas at Austin.

Edited by:

Mandy Armitage, MD

Mandy Armitage, MD, has combined her interests in clinical medicine with her passion for education and content development for many years. She served as medical director for the health technology companies HealthLoop (now Get Well) and Doximity.

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