Overview

Neuroendocrine tumors (NETs) are a group of uncommon tumors that start in your neuroendocrine cells. These cells combine the traits of nerve cells and hormone-producing endocrine cells. Most neuroendocrine tumors are malignant (cancerous).

There are several types of neuroendocrine tumors with symptoms that are easy to mistake for other less serious conditions. The characteristics of NETs — including how aggressive (fast-growing) they are, the symptoms they cause and what treatments work best — vary significantly based on the tumor.

Types of neuroendocrine tumors

Researchers classify NETs based on whether they release hormones:

  • Functional NETs release hormones and can cause hormone-related symptoms.
  • Non-functional NETs don’t release hormones. They can still cause symptoms if they impact an organ.

Researchers also classify neuroendocrine tumors based on where the tumor starts in your body. The most common types include:

  • Gastrointestinal neuroendocrine tumors (GI-NETs): NETs most commonly start in your gastrointestinal (GI) tract. Most start in your intestines, rectum or appendix. GI-NETs used to be called carcinoid tumors.
  • Lung neuroendocrine tumors: These tumors start in your lungs or bronchi, the tubes that carry air from your windpipe to your lungs. They’re the second most common type of NET and were also once called carcinoid tumors.
  • Pancreatic neuroendocrine tumors (P-NETs): These tumors start in your pancreas and are a type of pancreatic cancer. P-NETs are the third most common type of NET.

Less often, NETs may start in your:

  • Thyroid gland.
  • Parathyroid glands.
  • Pituitary gland.
  • Adrenal glands.
  • Thymus.

How common are neuroendocrine tumors?

NETs affect about 6 in 100,000 people worldwide. Although neuroendocrine cancer is rare, more people are being diagnosed. This is likely thanks to improved diagnostic tests that identify NETs more quickly.

Although anyone can develop neuroendocrine tumors, they’re rare in children, teens and young adults. On average, most people diagnosed are between the ages of 50 and 60.

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