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.

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.

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.

The risk of neuroendocrine tumors is higher in people who inherit genetic syndromes that increase the risk of cancer. Examples include:

• Multiple endocrine neoplasia, type 1 (MEN 1).
• Multiple endocrine neoplasia, type 2 (MEN 2).
• Von Hippel-Lindau disease.
• Tuberous sclerosis.
• Neurofibromatosis.

Neuroendocrine tumor diagnosis often starts with an exam. A healthcare professional might check your body for signs of cancer. Other tests and procedures might include blood and urine tests, imaging tests and a biopsy procedure.

Physical exam

A healthcare professional may examine your body to better understand your condition. The healthcare professional may feel for swollen lymph nodes or look for signs that a neuroendocrine tumor is producing excess hormones. The health professional may ask about your symptoms.

Tests to look for excess hormones

Neuroendocrine tumors sometimes make excess hormones. Your healthcare professional may recommend testing your blood or your urine for signs of extra hormones.

Imaging tests

Imaging tests make pictures of the inside of the body. For neuroendocrine tumors, imaging tests can make pictures that show the cancer's location and size. If there's a risk that the cancer may have spread, imaging tests can look for that too. Imaging tests might include:

• Ultrasound.
• Computerized tomography (CT) scan.
• Magnetic resonance imaging (MRI) scan.
• Positron emission tomography (PET) scan with a tracer that attaches to cells with receptors for a chemical called somatostatin, which neuroendocrine tumor cells often have. This kind of PET scan is sometimes called a somatostatin receptor (SSTR) PET scan. The tracer contains a medicine called dotatate, so this kind of scan also is called a dotatate PET scan.

Biopsy

A biopsy is a procedure to remove a sample of tissue for testing in a lab. In the lab, tests can show whether cancer cells are present. How a biopsy is done for a neuroendocrine tumor depends on where the cancer is in the body.

To collect the cells, a healthcare professional might use a long, thin tube with a light and a camera on the end. The tube can go down the throat to collect tissue from a lung tumor. This procedure is called bronchoscopy. The tube can go through the anus to get tissue from a tumor in the colon or rectum. This procedure is called colonoscopy. Sometimes, collecting a tissue sample requires surgery.

Examining the cancer cells

Healthcare professionals in the lab look at the neuroendocrine tumor cells with a microscope to decide if they are well differentiated or poorly differentiated. These terms describe how much the cancer cells look like healthy cells.

• Well-differentiated neuroendocrine tumors have cells that look similar to healthy cells. This usually means the cancer grows more slowly and is less aggressive. Well-differentiated cancers can still grow large and spread to other parts of the body, but they are less likely to do so. Healthcare professionals sometimes call these cancers carcinoid tumors.
• Poorly differentiated neuroendocrine tumors have cells that look different from healthy cells. This usually means the cancer grows quickly and is more aggressive. Healthcare professionals also call these cancers neuroendocrine carcinomas (NECs).

The differentiation tells the healthcare team about how the cancer is likely to act. It helps the healthcare team understand the prognosis and choose a treatment.

Measuring how fast the cancer cells are growing

Lab tests also can show how fast the cancer cells are growing and dividing. This is called the cancer's grade. The grade tells the healthcare team how the cancer is likely to behave.

To find the grade, healthcare professionals in the lab look at the cancer cells with a microscope. They count how many of the cells are dividing, called the mitotic rate. They also measure how many cells are actively growing, called the Ki-67 score.

Neuroendocrine tumor grades go from 1 to 3.

• Grade 1. These cancers are considered low grade. They tend to grow slowly.
• Grade 2. These cancers are considered intermediate grade. They usually grow and spread faster than grade 1 but slower than grade 3.
• Grade 3. These cancers are considered high grade. They tend to grow quickly.

The grade helps the healthcare team understand the prognosis and choose a treatment.

Neuroendocrine tumor treatments include surgery, radiation therapy and medicines, such as chemotherapy, targeted therapy and immunotherapy. If the cancer is making excess hormones, medicines can help control the symptoms the hormones cause.

Your healthcare team considers many factors when creating your treatment plan. They might consider the type of tumor, its location and whether you're experiencing symptoms.

Surgery

Surgery is used to remove the neuroendocrine tumor. When possible, surgeons work to remove all of the cancer and some of the healthy tissue that surrounds it, called the margin. Removing the margin helps ensure that all the cancer cells are removed. If the cancer can't be removed completely, it might help to remove as much of it as possible.

Chemotherapy

Chemotherapy treats cancer with strong medicines. Many chemotherapy medicines exist. Most chemotherapy medicines are given through a vein. Some come in pill form.

For neuroendocrine tumors, chemotherapy might be the first treatment if surgery isn't possible. It can help treat cancer that spreads.

Chemotherapy is sometimes used before surgery to shrink the neuroendocrine tumor. This can make it easier to remove. Chemotherapy may be used after surgery to kill any cancer cells that may remain.

Targeted therapy

Targeted therapy for cancer is a treatment that uses medicines that attack specific chemicals in the cancer cells. By blocking these chemicals, targeted treatments can cause cancer cells to die. Your cancer cells may be tested to see if targeted therapy is likely to be effective. One medicine that works in this way is everolimus (Afinitor).

For neuroendocrine tumors, targeted therapy might be used for cancers that can't be removed with surgery and cancers that spread.

Medicines to control excess hormones

If your neuroendocrine tumor releases excess hormones, your healthcare professional might recommend medicines to control the hormones. Medicines that work in this way are called somatostatin analog medicines. Examples include octreotide (Bynfezia Pen, Sandostatin) and lanreotide (Somatuline Depot). They can help with symptoms.

Immunotherapy

Immunotherapy for cancer is a treatment with medicine that helps the body's immune system kill cancer cells. The immune system fights off diseases by attacking germs and other cells that shouldn't be in the body. Cancer cells survive by hiding from the immune system. Immunotherapy helps the immune system cells find and kill the cancer cells. One medicine that works in this way is pembrolizumab (Keytruda).

For neuroendocrine tumors, immunotherapy might be an option for treating advanced cancers.

Radiation therapy

Radiation therapy treats cancer with powerful energy. Radiation treatments used for neuroendocrine tumors include:

• External beam radiation therapy. This treatment uses beams of energy that can come from X-rays, protons or other sources. During external beam radiation therapy, you lie on a table while a machine moves around you. The machine directs radiation to precise points on your body. Some types of neuroendocrine tumors may respond to this treatment. It might be recommended if surgery isn't an option.
• Peptide receptor radionuclide therapy. Peptide receptor radionuclide therapy uses a radiopharmaceutical to treat cancer. A radiopharmaceutical is a medicine that combines a medicine that targets cancer cells with a small amount of a radioactive substance. It allows radiation to be delivered directly to the cancer cells. One medicine that works in this way is lutetium Lu 177 dotatate (Lutathera). It is used to treat advanced neuroendocrine tumors.

Coping with a neuroendocrine tumor diagnosis can be challenging. Some people say they felt shocked or worried when they found out they had a neuroendocrine tumor. A cancer diagnosis can bring up many emotions. With time, you'll find ways to cope with these feelings. Until then, here are some ideas for what to do next.

Learn enough about neuroendocrine tumors to make treatment decisions

Make a list of questions to ask at your next appointment. Bring a trusted person to help you take notes. Ask your healthcare team about reliable places to turn to for accurate information. The more you know about your cancer and your treatment options, the more confident you may feel as you make treatment decisions.

Connect with others with neuroendocrine tumors

Consider joining a support group, either in your community or online. A support group of people with the same diagnosis can be a source of useful information, practical tips and encouragement.

Ask your healthcare team about support groups in your area or contact the American Cancer Society. Find support online through Mayo Clinic Connect, which is a community where you can connect with others for support, practical information and answers to everyday questions.

Take time for yourself

Set aside time for yourself each day. Use this time to take your mind off your cancer and do what makes you happy. Even a short break for some relaxation in the middle of a day full of tests and scans may help you cope.

Find a good listener

Finding someone who is willing to listen to you talk about your hopes and fears can be helpful as you manage a cancer diagnosis. This could be a friend or family member. A counselor, medical social worker or clergy member also may offer helpful guidance and care.

Start by making an appointment with a doctor or other healthcare professional if you have any symptoms that worry you. If your healthcare professional thinks you might have a neuroendocrine tumor, that person will likely refer you to a specialist. The kind of specialist you see might depend on the part of the body that is affected. You might see a doctor who specializes in treating cancer, called an oncologist.

Because appointments can be brief, it's a good idea to be prepared. Here's some information to help you get ready and know what to expect from your doctor.

What you can do

• Be aware of any restrictions before your appointment. At the time you make the appointment, be sure to ask if there's anything you need to do in advance, such as change your diet.
• Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
• Write down key personal information, including any major stresses or recent life changes.
• Make a list of all medicines, vitamins or supplements you're taking and the doses.
• Consider taking a family member or friend along. Sometimes it can be hard to remember all the information provided during an appointment. Someone who comes with you may remember something that you missed or forgot.
• Write down questions to ask your healthcare team.

Write down questions to ask your doctor

Your time with your healthcare team is limited, so prepare a list of questions to help you make the most of your time together. List your questions from most important to least important in case time runs out. For neuroendocrine tumors, some basic questions to ask include:

• What may be causing my symptoms or condition?
• What kinds of tests do I need?
• What do you recommend for next steps in determining my diagnosis and treatment?
• What are the alternatives to the approach that you're suggesting?
• Do I need to start treatment right away?
• What are the possible side effects of treatment?
• I have these other health conditions. How can I best treat them together?
• Are there any restrictions that I need to follow?
• Should I see a specialist?
• Where can I find more information?

In addition to the questions that you've prepared, don't hesitate to ask other questions during your appointment.

What to expect from your doctor

Your healthcare team is likely to ask you questions, such as:

• When did you first begin experiencing symptoms?
• How have your symptoms changed over time?
• How severe are your symptoms?
• What, if anything, seems to improve your symptoms?
• What, if anything, appears to worsen your symptoms?

After the healthcare team confirms a diagnosis of neuroendocrine tumor, the next step is to find the cancer's stage. The stage of a neuroendocrine tumor tells the healthcare team about the size of the cancer. It also tells the care team whether the cancer has spread to nearby lymph nodes or to other parts of the body.

The cancer's stage gives healthcare teams a shared way of describing the cancer. The care team uses the stage to help choose the treatment plan. It also gives the care team a general understanding of the prognosis of the cancer.

Staging tests

To find the stage, the healthcare team uses the results of tests and procedures, including:

• Imaging tests. Imaging tests may include CT, MRI and PET scans. These tests can show the size of the cancer and whether it has spread in the body. Healthcare teams use this information to decide on the stage.
• Biopsy. A biopsy collects a sample of tissue for testing in a lab. Tests can show whether the cancer cells are well differentiated or poorly differentiated. This helps the healthcare team decide what set of stages to use for the cancer.

Healthcare professionals use specific stages for some well-differentiated neuroendocrine tumors. These tumors tend to grow slowly and act in a unique way, so they are staged separately from other cancers.

Poorly differentiated neuroendocrine tumors don't have specific stages. Instead, these cancers are staged using the stages for the organ in which they start. For example, poorly differentiated pancreatic neuroendocrine tumors tend to grow quickly. They act like other kinds of pancreatic cancer, so the staging follows the stages for pancreatic cancer.

The stages of neuroendocrine tumors aren't affected by whether the cancer is functional or nonfunctional. A functional neuroendocrine tumor makes hormones that cause symptoms. A nonfunctional neuroendocrine tumor doesn't make hormones or doesn't make enough to cause symptoms.

The stages also aren't affected by cancer grade. The grade tells the healthcare team how quickly the cancer is growing.

Pancreas neuroendocrine tumors

The stages for pancreatic neuroendocrine tumors only apply to well-differentiated cancers. Poorly differentiated pancreatic neuroendocrine tumors use the same stages that are used for pancreatic cancer in general.

The stages of well-differentiated pancreatic neuroendocrine tumors range from 1 to 4. A lower stage means the cancer is smaller and only in the pancreas. As the cancer grows or spreads, the stages get higher.

• Stage 1. A stage 1 pancreatic neuroendocrine tumor is small and only in the pancreas. The cancer is less than 2 centimeters (about 3/4 inch) at its widest point.
• Stage 2. A stage 2 cancer may still only be in the pancreas, but it is larger than stage 1. At this stage, the cancer may have grown to invade structures near the pancreas, such as the small intestine or the bile duct.
• Stage 3. A stage 3 cancer may be a large cancer that has grown to invade other structures near the pancreas. It might grow beyond the pancreas and into the stomach, spleen, colon or major blood vessels. A stage 3 cancer also can be any size cancer that spreads to the nearby lymph nodes.
• Stage 4. A stage 4 pancreatic neuroendocrine tumor is any cancer that spreads to other parts of the body. This cancer most often spreads to the liver. It also can spread to the lungs, bones, peritoneum and distant lymph nodes.

Colon and rectum neuroendocrine tumors

The stages for neuroendocrine tumors of the colon and rectum only apply to well-differentiated cancers. Poorly differentiated colon and rectum neuroendocrine tumors use the same stages that are used for colon cancer and rectal cancer in general.

The stages of well-differentiated colon and rectal neuroendocrine tumors range from 1 to 4. A lower stage means the cancer is small and limited to the inner layers of the colon or rectum. As the cancer grows or spreads, the stages get higher.

• Stage 1. A stage 1 neuroendocrine tumor in the colon or rectum is small and only affects the innermost layers of the colon or rectum. The cancer is less than 2 centimeters (about 3/4 inch) at its widest point.
• Stage 2. A stage 2 cancer may be larger than 2 centimeters. It also may be a cancer that extends deeper into the wall of the colon or rectum.
• Stage 3. A stage 3 cancer may be large and may have grown through the wall of the colon or rectum. This stage also includes any cancer that has spread to nearby lymph nodes.
• Stage 4. A stage 4 neuroendocrine tumor in the colon or rectum has spread to other parts of the body. This cancer most often spreads to the liver, peritoneum and distant lymph nodes. It also can spread to the bones, lungs and other parts of the body.

Small intestine neuroendocrine tumors

The stages for neuroendocrine tumors of the small intestine only apply to well-differentiated cancers. Poorly differentiated small intestine neuroendocrine tumors are staged using the stages for small intestine cancer in general.

The stages of well-differentiated small intestine neuroendocrine tumors range from 1 to 4. A lower stage means the cancer is small and limited to the intestine. As the cancer grows or spreads, the stages get higher.

• Stage 1. A stage 1 small intestine neuroendocrine tumor is small and only affects the inner layers of the intestine. The cancer is less than 1 centimeter (a little less than 1/2 inch) at its widest point.
• Stage 2. A stage 2 cancer may be larger than 1 centimeter or it may grow deeper into the wall of the intestine.
• Stage 3. A stage 3 cancer may have grown through the wall of the intestine. This stage also includes any cancer that has spread to nearby lymph nodes.
• Stage 4. A stage 4 small intestine neuroendocrine tumor has spread to other parts of the body. This cancer most often spreads to the liver and peritoneum. It also can spread to bones, lungs and distant lymph nodes.

Appendix neuroendocrine tumors

The stages for appendix neuroendocrine tumors only apply to well-differentiated cancers. Poorly differentiated neuroendocrine tumors of the appendix are staged differently, using the system for appendix cancer in general.

The stages of well-differentiated appendix neuroendocrine tumors range from 1 to 4. A lower stage means the cancer is small and limited to the appendix. As the cancer grows or spreads, the stages get higher.

• Stage 1. A stage 1 appendix neuroendocrine tumor is small and only in the appendix. The cancer is 2 centimeters (about 3/4 inch) or smaller at its widest point.
• Stage 2. A stage 2 cancer is larger than 2 centimeters, or it has grown deeper into the wall of the appendix. It has not spread to lymph nodes or to other parts of the body.
• Stage 3. A stage 3 cancer may be large and may have grown beyond the appendix. This stage also includes any cancer that has spread to nearby lymph nodes.
• Stage 4. A stage 4 appendix neuroendocrine tumor has spread to other parts of the body. This cancer most often spreads to the distant lymph nodes, liver, lungs and bones.

Lung neuroendocrine tumors

There are no specific stages for lung neuroendocrine tumors. Instead, these cancers use the staging for lung cancer in general. Types of lung cancer that are neuroendocrine tumors include small cell lung cancer, large cell neuroendocrine tumor and carcinoid tumor.

Survival rates for neuroendocrine tumors vary greatly. This cancer can happen just about anywhere in the body. It sometimes grows so slowly that it doesn't need treatment right away, and treatment might involve close monitoring. But other times it can grow quickly and act aggressively.

This makes it hard to understand what general neuroendocrine tumor survival rates might mean for you. Still, many people want to know the survival rates to help them understand how to talk about the prognosis with their healthcare professionals.

One study of neuroendocrine tumor survival rates looked at people in the United States diagnosed between 2000 and 2021. It reported survival rates by extent of disease.

• Localized neuroendocrine tumors had a five-year overall survival rate of about 90%. This means that for every 100 people included in the study, 90 were still living five years after diagnosis. Localized means the cancer hasn't grown beyond the place where it started and it hasn't spread. This is usually a stage 1 or stage 2 neuroendocrine tumor.
• Regional neuroendocrine tumors had a five-year overall survival rate of about 85%. Regional means the cancer has spread to nearby lymph nodes. This usually is a stage 3 neuroendocrine tumor.
• Distant neuroendocrine tumors had a five-year overall survival rate of about 57%. Distant means the cancer has spread to other parts of the body. This is usually a stage 4 neuroendocrine tumor.

Survival rates can give you an idea about the outlook for someone with a neuroendocrine tumor, but they can't say exactly how long you will live. Many factors affect prognosis and survival rates for neuroendocrine tumors, including:

• Location. Survival rates for neuroendocrine tumors vary by the cancer's location. Neuroendocrine tumors in the appendix and the rectum tend to have a better prognosis, while those in the pancreas and lungs tend to have a worse prognosis.
• Size. Small neuroendocrine tumors are often easier to remove with surgery and have a better prognosis. If the cancer grows into nearby structures, surgery might not be possible or might be more complex.
• Spread. In general, stage 4 neuroendocrine tumors that spread to other parts of the body have a worse prognosis.
• Differentiation. Well-differentiated neuroendocrine tumors tend to grow more slowly and are less likely to spread. They have a better prognosis than poorly differentiated neuroendocrine tumors.
• Grade. Low-grade neuroendocrine tumors have the best prognosis because they usually grow slowly. Intermediate grade and high-grade cancers have a worse prognosis. Healthcare professionals decide on the grade using the Ki-67 score and mitotic rate. If these numbers are high, it's a sign that the cancer is growing quickly and the survival rate may be lower.
• Somatostatin receptors. Somatostatin receptors are found on the outside of many neuroendocrine tumor cells. Having cancer cells with somatostatin receptor type 2 (SSTR2) on their surface may give a better prognosis because there are more treatment options. Treatments that can target these cells include somatostatin analog medicines and radiopharmaceutical therapy.
• Functional status. It's not clear whether a functional neuroendocrine tumor gives a worse or better prognosis compared to a nonfunctional cancer. Functional cancers make extra hormones that cause symptoms, which can sometimes be bothersome or even cause serious complications. These symptoms may affect quality of life, but it isn't clear whether they change survival rates.
• Your overall health. Healthcare teams consider your overall health when making a treatment plan. If you have other serious health concerns, this could limit your treatment options and lead to a worse prognosis.

If you want to know the survival rate for your neuroendocrine tumor, talk about it with your healthcare team. Your care team can tell you about the prognosis for someone in your particular situation. Team members also know more about you and your cancer and can explain what may affect your personal outlook.