Overview
Neuroendocrine tumors are cancers that start in neuroendocrine cells. Neuroendocrine cells have traits similar to nerve cells, which send and receive signals from the brain, and endocrine cells, which make hormones that regulate various body functions.
Neuroendocrine tumors are rare. They can happen anywhere in the body. Most neuroendocrine tumors occur in the lungs, appendix, small intestine, rectum and pancreas.
There are many types of neuroendocrine tumors. Some grow slowly and some grow very quickly. Some are functional neuroendocrine tumors, which means they make excess hormones. Others are nonfunctional neuroendocrine tumors, which means they don't release hormones or don't release enough to cause symptoms.
Diagnosis and treatment of neuroendocrine tumors depend on various factors. These include the type of tumor, its location, whether it produces excess hormones, how aggressive it is and whether it has spread to other parts of the body.
Some people wonder if neuroendocrine tumors are related to adenocarcinoma. Adenocarcinoma is cancer that starts in gland cells. Adenocarcinomas are similar to neuroendocrine tumors in that they can happen just about anywhere in the body. But they are different types of cancer that behave differently. For example, pancreatic neuroendocrine tumors tend to grow more slowly than pancreatic adenocarcinomas. Pancreatic neuroendocrine tumors have a better prognosis.
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Types
Symptoms
Neuroendocrine tumors don't always cause signs and symptoms at first. Symptoms can depend on the location of the tumor and whether it produces excess hormones.
In general, neuroendocrine tumor symptoms might include:
- Pain from a growing tumor.
- A growing lump you can feel under the skin.
- Feeling very tired.
- Losing weight without trying.
Some neuroendocrine tumors make excess hormones. These tumors are called functioning neuroendocrine tumors. Symptoms of these tumors can include:
- Skin flushing.
- Diarrhea.
- Increased thirst.
- Dizziness.
- Shakiness.
- Skin rash.
When to see a doctor
Make an appointment with a doctor or other healthcare professional if you have any symptoms that worry you.
Causes
The exact cause of neuroendocrine tumors isn't known. These cancers begin in neuroendocrine cells, which are found throughout the body. Neuroendocrine cells have traits similar to nerve cells, which send and receive signals from the brain, and to endocrine cells, which make hormones that regulate various body functions.
Neuroendocrine tumors happen when neuroendocrine cells get changes in their DNA. A cell's DNA holds the instructions that tell the cell what to do. In healthy cells, the DNA tells the cells to grow and multiply at a set rate. The DNA also tells the cells to die at a set time.
In cancer cells, the DNA changes give other instructions. The changes tell the cancer cells to grow and multiply quickly. Cancer cells can keep living when healthy cells would die. This causes too many cells.
The cancer cells might form a mass called a tumor. The tumor can grow to invade and destroy healthy body tissue. In time, cancer cells can break away and spread to other parts of the body. When cancer spreads, it's called metastatic cancer.
Risk factors
The risk of neuroendocrine tumors is higher in people who inherit genetic syndromes that increase the risk of cancer. Examples include:
Oct. 18, 2025