What is neuroendocrine tumors (NETs)?

Neuroendocrine cells are special cells spread all through the body. They act a bit like nerve cells and a bit like hormone-making cells. They release hormones and other chemicals that help control things like digestion and blood sugar. A neuroendocrine tumor, or NET, starts when these cells grow out of control. NETs can start almost anywhere. The most common places are the small intestine, the pancreas, the lungs, the rectum, the appendix, and the stomach. You may also hear the older name carcinoid tumor.

When should I call my care team?

Fever of 100.4 F (38 C) or higher, or shaking chills, especially after PRRT, chemotherapy, or while on everolimus; Severe flushing with dizziness, fainting, a racing heartbeat, or wheezing (possible carcinoid crisis); Diarrhea that will not stop, or diarrhea with dizziness, very little urine, or weakness; Shakiness, sweating, confusion, or fainting that may be low blood sugar, or a blood sugar reading that is very low; Severe belly pain with swelling, vomiting, or not passing gas or stool (possible bowel blockage); Black or bloody stools, or vomiting blood; New cough, shortness of breath, or chest pain; New swelling in the legs or belly, or getting short of breath easily (possible heart valve problem); Yellow skin or eyes, or very dark urine; Severe headache, vision changes, or a very high blood pressure reading while on sunitinib or cabozantinib.

Neuroendocrine tumors (NETs)

Neuroendocrine tumors often grow slowly, and many people live for years with them thanks to treatments that control both the tumor and its symptoms.

Hi, I'm Rosa. Today we'll go through neuroendocrine tumors together, one step at a time. I'll keep it simple, and you can pause me, go back, or skip ahead whenever you like. Just so you know, this is for learning only. It is not medical advice, so please check everything with your own doctor and care team. Okay, let's get started.

What these tumors are

Let's start with the basics. Your body has special cells called neuroendocrine cells. They act a bit like nerve cells and a bit like hormone cells. They help control things like digestion and blood sugar. A neuroendocrine tumor starts when these cells grow out of control. Doctors often call it a NET, spelled N, E, T. NETs can start in many places. The most common are the small intestine, the pancreas, and the lungs. Many NETs grow slowly. Some make extra hormones that cause symptoms. Many people live for years with good quality of life.

The main types

Let's talk briefly about the types. NETs are often named for where they start. Small intestine NETs are one of the most common. Pancreatic NETs are very different from the usual pancreas cancer. Lung NETs are also called carcinoids. Small NETs in the rectum, appendix, or stomach are often found early. Some NETs make hormones that cause symptoms. Doctors call these functional. Others do not, and are called nonfunctional. There is also a fast-growing kind called neuroendocrine carcinoma. Small cell lung cancer is in that group. It is treated differently.

Tests you may have

Now let's talk about tests. A biopsy takes a small piece of the tumor. The lab checks how fast the cells are growing. CT and MRI scans show where the tumor is. A special PET scan uses a tracer that sticks to NET cells. It finds spots well. It also shows if certain treatments may work. Urine or blood tests check for hormones the tumor may make. Before a urine test, you may need to skip some foods, like bananas and avocados. A camera test can look inside the gut. Some people get a heart ultrasound too.

Grade and stage

Next up, let's talk about grade and stage. The grade tells how fast the cells are growing. There are three grades. Grade one grows the slowest. Grade three grows the fastest. The stage tells how far the tumor has spread. It goes from stage one to stage four. The liver is the most common place NETs spread. Even when a NET has spread, it can often be controlled for years. These groups help your team plan treatment. They help everyone talk the same language. Your doctor will explain what yours mean for you.

Hormones and receptors

Before we move to treatment, there are some things to know. NETs can make hormones. These can cause flushing, diarrhea, or low blood sugar. Treating these hormones is a big part of care. Most NET cells also have docking spots called receptors. Several key treatments attach to these spots. So your team checks if your tumor has them. Some people are born with gene changes that raise NET risk. A gene test can check for these. Your doctor will tell you what your results mean. You can read more in the guide. The Questions to ask page can help you prepare.

Main treatment options

Now let's look at treatment. Surgery can cure many NETs that have not spread far. Some small, slow NETs can be watched with scans. Monthly shots called octreotide and lanreotide calm hormone symptoms. They also slow tumor growth. Another treatment sends radiation right to the NET cells through a vein. It is called PRRT, and it is given every few weeks. Some daily pills slow tumor growth too. Chemotherapy helps some people. Liver spots can be treated directly. Clinical trials are research studies that may offer new options. Ask your team about them.

Symptoms and what helps

Let's talk about symptoms and side effects. Flushing and diarrhea often get better with the monthly shots. Alcohol, spicy food, and stress can trigger flushing. The shots can cause loose stools and, over time, gallstones. The radiation treatment can cause nausea and lower blood counts for a while. Some pills cause mouth sores, high blood pressure, or sore hands and feet. Tell your team early, so they can help. If your tumor makes insulin, keep a sugar source with you. We have a whole side effects guide on this site.

Living well with a NET

Last, let's talk about living well. For many people, a NET is managed over many years. There can be long, stable stretches with just shots and scans. Try to be seen at least once at a center that treats many NETs. Before any surgery or procedure, tell the team you have a NET. Support groups can help you feel less alone. Call your care team right away for a fever. Call for severe flushing with dizziness, or diarrhea that will not stop. If it feels very bad, call 911. Also see our new Screening, prevention and survivorship section.

You did great today. Thank you for learning with me. Write down your questions and bring them to your next visit. Call your care team any time something worries you. Many people live well with a NET for a long time. You are not alone.

Call your care team right away if you have

Fever of 100.4 F (38 C) or higher, or shaking chills, especially after PRRT, chemotherapy, or while on everolimus
Severe flushing with dizziness, fainting, a racing heartbeat, or wheezing (possible carcinoid crisis)
Diarrhea that will not stop, or diarrhea with dizziness, very little urine, or weakness
Shakiness, sweating, confusion, or fainting that may be low blood sugar, or a blood sugar reading that is very low
Severe belly pain with swelling, vomiting, or not passing gas or stool (possible bowel blockage)
Black or bloody stools, or vomiting blood
New cough, shortness of breath, or chest pain
New swelling in the legs or belly, or getting short of breath easily (possible heart valve problem)
Yellow skin or eyes, or very dark urine
Severe headache, vision changes, or a very high blood pressure reading while on sunitinib or cabozantinib

Side effects: what helps

Sources

Quick answers

What is neuroendocrine tumors (NETs)?: Neuroendocrine cells are special cells spread all through the body. They act a bit like nerve cells and a bit like hormone-making cells. They release hormones and other chemicals that help control things like digestion and blood sugar. A neuroendocrine tumor, or NET, starts when these cells grow out of control. NETs can start almost anywhere. The most common places are the small intestine, the pancreas, the lungs, the rectum, the appendix, and the stomach. You may also hear the older name carcinoid tumor.
When should I call my care team?: Fever of 100.4 F (38 C) or higher, or shaking chills, especially after PRRT, chemotherapy, or while on everolimus; Severe flushing with dizziness, fainting, a racing heartbeat, or wheezing (possible carcinoid crisis); Diarrhea that will not stop, or diarrhea with dizziness, very little urine, or weakness; Shakiness, sweating, confusion, or fainting that may be low blood sugar, or a blood sugar reading that is very low; Severe belly pain with swelling, vomiting, or not passing gas or stool (possible bowel blockage); Black or bloody stools, or vomiting blood; New cough, shortness of breath, or chest pain; New swelling in the legs or belly, or getting short of breath easily (possible heart valve problem); Yellow skin or eyes, or very dark urine; Severe headache, vision changes, or a very high blood pressure reading while on sunitinib or cabozantinib.

Last updated: 2026-10-27. Medically reviewed by Veli Bakalov, MD, medical oncologist (October 2026). General education from Step by Step, the patient portal of HemeOncBuddy.