Neuroendocrine tumors (NETs)

A neuroendocrine tumor (NET) is an uncommon cancer type that forms in neuroendocrine cells

What is a Neuroendocrine Tumor?

Neuroendocrine tumours (NETs) arise from cells that produce and secrete a variety of hormones, which are found in many different parts of the body, including the:

  • Gastrointestinal (GI) tract. NETs develop most commonly in the GI tract or digestive system, specifically the small intestine and appendix. The GI tract plays a central role in digesting foods and liquid and in processing waste. GI tract NETs also used to be called carcinoid tumors.
  • Pancreas. Approximately 7% of NETs can develop in the pancreas, a pear-shaped gland located in the abdomen between the stomach and the spine. Pancreas NETs used to be called islet cell tumors.
  • Lung. The lung is the second most common location of NETs. About 30% of NETs occur in the bronchial system, which carries air to the lungs. Lung NETs used to be called carcinoid tumors


The symptoms you might experience depend on the location of your tumor and whether the NET is functional or nonfunctional. unctioning NETs are defined based on the presence of clinical symptoms due to excess hormone secretion by the tumor. Nonfunctional NETs do not secrete hormones. They may produce symptoms caused by the tumor's growth.

In general, neuroendocrine tumor signs and symptoms might include:

  • Pain from a growing tumor
  • A growing lump you can feel under the skin
  • Fatigue
  • Loss of appetite

Neuroendocrine tumors that produce excess hormones (functional tumors) might cause:

  • Flushing in the face or neck, usually without sweating
  • Diarrhea
  • Frequent urination
  • Increased thirst
  • Dizziness
  • Seizures
  • Shakiness
  • Skin rash

Risk Factors

What causes NETs is unknown, and no avoidable risk factors have been found. However, the following factors may raise a person’s risk for developing a NET:

  • Inherited syndromes: Multiple endocrine neoplasia, type 1 (MEN 1), Multiple endocrine neoplasia, type 2 (MEN 2) and Von Hippel-Lindau disease are hereditary condition associated with NETs
  • Tuberous sclerosis
  • Neurofibromatosis


If your doctor suspects a NET, he or she will ask for a complete medical and family history and perform a thorough physical examination. In addition, the following tests may be used to diagnose a NET:

  • Blood/urine tests: Your doctor may recommend testing your blood or your urine for signs of excess hormones that are sometimes produced by neuroendocrine tumors.
  • Imaging tests: You might undergo imaging tests, such as ultrasound, CT and MRI, to create pictures of your tumor. For neuroendocrine tumors, pictures are sometimes created using positron emission tomography (PET) with a radioactive tracer that's injected into a vein.
  • Biopsy: To collect the cells, the doctor might insert a long, thin tube with a light and a camera on the end into your lungs (bronchoscopy), your esophagus (endoscopy) or your rectum (colonoscopy), depending on your situation.


The treatment options for your neuroendocrine tumor will depend on the type of tumor, its location, and whether you're experiencing signs and symptoms of excess hormones produced by the tumor.

In general, neuroendocrine tumor treatment options might include:

  • Surgery. Surgery is used to remove the tumor and is often the first line treatment for patients with localized NETs. When possible, surgeons work to remove the entire tumor and some of the healthy tissue that surrounds it, called a margin, in an effort to leave no traces of cancer in the body.
  • Chemotherapy. Chemotherapy uses drugs to kill tumor cells. Chemotherapy might be recommended if there's a risk that your neuroendocrine tumor might recur after surgery. It might also be used for advanced tumors that can't be removed with surgery or the tumour has spread from where it started to other organs.
  • Targeted drug therapy. Targeted drug treatments focus on specific abnormalities present within tumor cells. By blocking these abnormalities, targeted drug treatments can cause tumor cells to die. Targeted drug therapy is usually combined with chemotherapy for advanced neuroendocrine tumors. Everolimus (Afinitor) is a targeted therapy approved by the U.S. Food and Drug Administration (FDA) for the treatment of advanced NETs of the GI tract, lung, and pancreas.
  • Peptide receptor radionuclide therapy (PRRT). PRRT combines a drug that targets cancer cells with a small amount of a radioactive substance. It allows radiation to be delivered directly to the cancer cells. One PRRT drug, lutetium Lu 177 dotatate (Lutathera), is used to treat advanced neuroendocrine tumors.
  • Medications to control excess hormones. If your neuroendocrine tumor releases excess hormones, your doctor might recommend medications to control symptoms created by the hormones-like substances released by a NET.
  • Radiation therapy. Radiation therapy uses high energy X-rays to kill tumor cells. Some types of neuroendocrine tumors may respond to radiation therapy. It might be recommended if surgery isn't an option.