The short answer
Neuroendocrine tumors (NETs) are uncommon growths that start in hormone-producing cells found throughout the body, most often in the digestive tract. Many grow slowly. Some release hormones that cause symptoms like flushing or diarrhea, while others cause none. Treatment is mainly surgery, with hormone therapy and other options.
NETs start in hormone-making (neuroendocrine) cells found around the body.
NCI says GI NETs most often occur in the small intestine, appendix, and rectum.
NCI says GI NETs are typically slow-growing.
Some release hormones causing symptoms like flushing or diarrhea.
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This page explains what neuroendocrine tumors are, why their grade matters, and how they are treated.
What makes these tumors different
Neuroendocrine tumors, or NETs, start in hormone-making cells. These cells sit throughout the body. NCI's GI page says GI NETs most often occur in the small intestine, appendix, and rectum. NETs can also start in places such as the lungs and pancreas. That is why NETs can turn up in so many different organs. Older writing often calls some of these tumors carcinoid tumors.
Why grade matters more than usual here
Stage means how far a cancer has spread. Grade is also used to describe NETs.
Grade is a measure of how fast tumor cells divide. Lower-grade tumors tend to grow more slowly and higher-grade ones faster. NCI says GI NETs are typically slow-growing. Ask your care team what grade your tumor is and what that means for treatment.
Carcinoid syndrome: when the tumor releases hormones
Some NETs release hormones directly into the bloodstream, including a hormone called serotonin. When that happens, it can cause a cluster of symptoms called carcinoid syndrome:
- Redness or a feeling of warmth in the face and neck, often called flushing.
- Diarrhea, abdominal pain, or a bloated feeling.
- Wheezing or other trouble breathing.
- A fast heartbeat.
NCI says liver enzymes usually destroy the hormones these tumors make. When a tumor has spread to the liver, the enzymes cannot clear the extra hormones, and they circulate through the body. Ask your team what your symptoms mean.
How NETs are treated
Treatment depends heavily on grade, location, and whether the tumor is producing hormones. Surgery to remove the tumor is often possible. NCI lists surgery as the main treatment for GI NETs. Hormone therapy with somatostatin analogs can help manage symptoms. In some cases, monitoring is used. For advanced disease, chemotherapy, radiation, and liver-directed procedures may be considered. Newer targeted therapies are in clinical trials. Ask your team which fits your tumor.
What to ask your team
- What grade is my tumor, and what does it mean for treatment?
- Is my tumor producing hormones, and do I have or am I at risk for carcinoid syndrome?
- Is surgery an option, or is monitoring the better approach right now?
- If I have carcinoid syndrome symptoms, what should prompt me to call you?
Sources
Common questions
What are neuroendocrine tumors?
Uncommon growths that start in hormone-making cells found throughout the body, most often in the digestive tract.
Are NETs slow-growing?
NCI says GI NETs are typically slow-growing. Grade and stage help describe how a particular NET behaves.
Why do some cause symptoms and others not?
Functioning NETs release hormones that cause symptoms like flushing or diarrhea, while non-functioning NETs cause no hormone symptoms.
How are they treated?
Depending on type and stage, treatment can include surgery, hormone-based medicines, monitoring, chemotherapy, and other options. Ask your team which fits.
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Sources last checked: 2026-08-13 what this meansLast updated: 2026-10-02Next planned review: 2027-07-12
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