Neuroendocrine Tumors : Types, Symptoms, Causes, Risks, Treatment and Diagnosis

There are many types of neuroendocrine tumors, and they can show up in many different parts of the body. A tumor begins in the body when the DNA of healthy cells get damaged. This causes the cells to change, and they start to grow out of control, creating a mass. A tumor can either be cancerous or benign. A cancerous tumor is malignant, which means that it will continue to grow and spread to other parts of the body if it is not detected early and treated. A benign tumor, on the other hand, means that the tumor can grow, but it is not likely to spread. It is usually possible to remove a benign tumor without causing much harm.

What is a Neuroendocrine Tumor?

A neuroendocrine tumor starts to develop in the specialized cells of the body’s neuroendocrine system, known as neuroendocrine cells. Neuroendocrine cells have similar characteristics to the nerve cells and the hormone-producing cells in the body and release hormones into the bloodstream in response to the signals from the nervous system. Because a neuroendocrine tumor arises from the cells that manufacture hormones in the body, the tumor itself is capable of producing hormones.1

What is a Neuroendocrine Tumor?

Neuroendocrine tumors are rare, but they can develop anywhere in the body. Most of the time, neuroendocrine tumors tend to grow in the lungs, stomach, small intestine, or the digestive tract, appendix, rectum, and pancreas. They can also develop in a small organ located behind the breast bone, known as the thymus.2 In rare cases, they can also grow in the kidneys, testicles, or ovaries.

There are many types of neuroendocrine tumors, and they are generally named after the type of cells where they grow or the hormone they produce. While some grow slowly, some can grow very rapidly and spread to other parts. Some neuroendocrine tumors produce excessive hormones and are known as functional neuroendocrine tumors. Others do not release hormones, or they don’t release sufficient hormones to cause symptoms and are known as nonfunctional neuroendocrine tumors. The symptoms of a neuroendocrine tumor depend on the place where your tumor is growing and what type of tumor it is.3

Different Types of Neuroendocrine Tumors

There are many types of neuroendocrine tumors, and they are named as per the location where they grow. Some of these include:

Pancreatic neuroendocrine tumors grow in the pancreas. There are several types of pancreatic neuroendocrine tumors, including:4

  • Insulinomas – This is the most common type of pancreatic neuroendocrine tumor. Their cells produce insulin, which is the hormone that regulates blood sugar levels in the body. Most of the time, these tumors are not malignant.5
  • Glucagonomas – This type of neuroendocrine tumor produces glucagon, which is a hormone that increases the blood sugar levels in the body. Nearly half of all glucagonomas are cancerous, and they tend to spread to other parts of the body as well.6
  • Gastrinomas – This type of neuroendocrine tumor manufacture a hormone known as gastrin. Gastrin helps you digest food. Gastrinomas can develop if you suffer from a rare disorder known as Zollinger-Ellison syndrome. Nearly half of all these gastrinomas turn out to be cancerous, and they tend to spread easily around the body.7,8
  • Somatostatinomas – this form of neuroendocrine tumor produces too much of a chemical known as somatostatin, which impacts the manner in which the body makes other hormones.9
  • VIPomas – this type of neuroendocrine tumor manufacture a hormone that triggers the release of other hormones in the body, known as vasoactive intestinal peptides (VIP). Most of the time, VIPomas turn out to be malignant.

There are several other types of neuroendocrine tumors, such as:

  • Pheochromocytoma: This type of neuroendocrine tumor develops in the cells of the adrenal glands, which are located just above the kidneys. Pheochromocytoma produces the hormones noradrenaline and adrenaline, which increases your blood pressure and heart rate. Usually, this type of neuroendocrine tumor is benign.10
  • Medullary Carcinoma: This type of tumor develops in the thyroid gland, which is located on the base of the neck. This tumor grows in cells that manufacture a hormone that impacts the levels of calcium in the body.11

What are the Symptoms of a Neuroendocrine Tumor?

The symptoms of a neuroendocrine tumor depend on what type of tumor you have and where it is located in the body.

With a pancreatic neuroendocrine tumor, you may develop the following symptoms:

  • Blurry or double vision
  • Dizziness
  • Confusion
  • Diarrhea
  • Headache
  • Rash
  • A fast heartbeat
  • Feeling hungry more than usual
  • Shakiness
  • Sweating
  • Weakness
  • Stomach pain
  • Unintentional weight loss
  • An uncomfortable feeling of fullness or bloating after eating

Carcinoid tumors can cause the following symptoms:

  • Warm, red, itchy skin, usually on the face and neck
  • Pain in the chest
  • Coughing
  • Diarrhea
  • Trouble breathing
  • Stomach pain
  • Feeling sick or tired
  • Unintentional weight gain or loss

Other types of neuroendocrinal tumors may cause symptoms that include:

  • Bleeding
  • Appetite loss
  • Diarrhea
  • Coughing
  • Headache
  • Fever
  • Nausea and/or vomiting
  • A hoarse voice
  • A fast heart rate,
  • Night sweats
  • Sweating
  • Rash
  • Pain
  • Yellowish skin or eyes
  • Unintentional weight loss or gain
  • A lump growing under the skin

Any type of neuroendocrine tumors that produce an excess amount of hormones may also cause:

  • Frequent urination
  • Flushing of skin
  • Diarrhea
  • Increased thirst
  • Shakiness
  • Skin rash
  • Dizziness
  • Unusual tiredness
  • Lightheadedness
  • Pain in a specific area that does not go away
  • Backup of stomach acid into the throat
  • Cough
  • Headache
  • Trouble seeing
  • Fast heart rate
  • Raised, red rash around the mouth, on the lower leg, or anywhere where the skin rubs against skin.

What are the Causes and Risk Factors of Neuroendocrine Tumors?

Most of the time, doctors are not able to pinpoint the exact cause of neuroendocrine tumors. However, you are at a higher risk of getting these tumors if you have a family history of certain diseases, including:

  • Neurofibromatosis type 1 – this condition makes you prone to tumors in the adrenal glands.12
  • Multiple endocrine neoplasia type 1 – this condition causes tumors to develop in the pancreas and other organs.13,14
  • Multiple endocrine neoplasia type 2
  • Von Hippel-Lindau syndrome – this causes tumors and fluid-filled sacs to develop in several parts of the body.15
  • Tuberous sclerosis

How are Neuroendocrine Tumors Diagnosed?

When you visit your doctor, they will first carry out a thorough physical examination, and they will ask you detailed questions about your symptoms. Your doctor will also prescribe different diagnostic tests to check for the tumor in your body. You may be prescribed the following diagnostic tests:

  • Urine and blood tests: These tests are used to check the levels of hormones in the body to check if they are too low or too high.
  • CT scan: This is a type of powerful X-ray that provides detailed pictures from inside the body.
  • MRI: MRI makes use of powerful magnets and radio waves to create pictures of your organs.
  • X-ray: X-ray uses radiation in low doses to see the insides of your body.
  • Biopsy: In a biopsy, they will take a small piece of tissue from the body and analyze it under a microscope to look for tumor cells. Doctors may also use a CT scan to help locate the right area. Or doctors may also use a tin, flexible that has a small came, known as an endoscope, attached at one end that offers a close-up look at the lining of the digestive tract. You may remain awake or asleep during the procedure, but some medication will be given to make you feel more comfortable.
  • Octreotide Scan: An octreotide scan is usually done in a hospital. You will be administered a shot of a tiny amount of a radioactive liquid through an IV, and you will be made to lie down in a scanner that will take images of your insides. The liquid given contains a drug known as octreotide that will stick to the cells that are present on the surface of most neuroendocrine tumors. You will have to get two scans over a period of two days, but you don’t need to spend the night in the hospital. Each scan will take up to three hours, but it will not hurt in any way.16
  • Molecular Testing: In this procedure, your doctor will check the samples of the tumor from the biopsy test and look for certain proteins, genes, and other substances that will help them decide what type of treatment to start you on.
  • PET Scan: In a positron emission tomography scan, there is a radioactive tracer injected that helps show any anomaly in the body when the scan takes place.

If these tests detect the tumor, you may need to undergo several other tests to determine the size of the tumor, stage of the spread, and what type of tumor it is. You may need to undergo the following tests:

  • Endoscopic ultrasound: Your doctor will insert a thin, flexible scope down your throat or into the rectum to take a look inside the body. There is a small device attached on one end of the scope that sends out high-energy sound waves that produce an image of your organs, including the lymph nodes and pancreas.17
  • Somatostatin Receptor Scintigraphy: In this test, you will be injected with a small amount of radioactive hormone. This attaches to the tumor, helping your doctor see just how big it is.

And, of course, a biopsy may be conducted again.

What is the Treatment for Neuroendocrine Tumors?

There are a variety of treatment options for neuroendocrine tumors, including surgery, radiation, chemotherapy, and drugs. The treatment your doctor will decide together with you depends on several factors, including:

  • What kind of tumor you have, and how many there are
  • Whether the tumor is cancerous
  • If the tumor has spread to other parts of the body or not

The common treatments for neuroendocrine tumors are as follows.

1. Surgery

Surgery is the most common treatment for most neuroendocrine tumors. Surgery can help completely remove some neuroendocrine tumors, especially the ones that are not malignant and have not spread.

A surgeon is able to take out only the tumor, or they may just remove part or all of the organs that are affect and have a neuroendocrine tumor, like the stomach, liver, or pancreas.

In one type of surgery, known as radiofrequency ablation, your doctor will insert a probe into the tumor. The probe gives off high-energy radio waves, which kill off cancer cells in a particular area.

Another type of surgery, known as cryosurgery, sends extreme cold directly into the tumor with the help of a thin, hollow tube. For such operations, your doctor may use ultrasounds or MRI scans to guide where the probe needs to go.18

2. Chemotherapy

Chemotherapy makes use of medications to kill off the cancerous cells or to stop them from spreading to other parts. You can either take these drugs orally by mouth, or a doctor will inject the drugs into one of your veins. You may need to take just a single medicine, or you may require a combination of different ones for a couple of weeks.

Chemotherapy can cause certain side effects, though, including fatigue, vomiting, nausea, and hair loss, but they usually stop once the treatment is over. Chemotherapy drugs impact everyone differently, and your doctor will let you know about what to do to feel better while undergoing chemotherapy.19

3. Radiation Therapy

This treatment method makes use of high-energy X-rays to kill off the cancerous cells. You may get radiation therapy if your tumor has spread to more parts of the body or if it is located in a place where the doctors cannot reach with surgery.

Most of the time, radiation therapy is given from a machine placed outside of the body. In some cases, your doctor may also place radiation implants near the tumors that are inside the body.20

4. Hormone Therapy

Hormone therapy is a common treatment used for carcinoid neuroendocrine tumors. The treatment uses a man-made version of the somatostatin hormone. These medications prevent the tumor from manufacturing hormones that cause diarrhea and the other symptoms of carcinoid syndrome. They may also help shrink the tumor.

5. Embolization Therapy

Embolization therapy can treat neuroendocrine tumors that have spread to the liver and cannot be removed with surgery. The goal of this treatment is to block the blood flow to the tumors that helps them grow.

This therapy will be done in a hospital, where a doctor will insert a thin, flexible tube known as a catheter into the artery that leads to the liver. Then, they will inject a substance that will plug up the artery. This procedure may also be combined with chemotherapy or radiation therapy.

6. Targeted Therapy

Targeted therapy uses medications that attack particular proteins or genes on the tumor cells to kill the cancer. This treatment restricts the damage caused to the healthy cells in the body, which is something that often happens with chemotherapy or radiation therapy.

Your doctor will decide on which drug would be the best for your condition after testing the cells from your tumor first. You may also need to take other medications to prevent the neuroendocrine tumors from growing, including hormones and drugs to slow down your heart and reduce the buildup of stomach acid.

Researchers are also searching for new ways to treat these tumors in various clinical trials. Clinical trials test out new drugs to see if they are safe to use and if they actually work. These trials can be a way for many people to try out certain new medicines that have not yet become available in the market. You need to talk to your doctor to find out if it’s a good idea to join a clinical trial.

Conclusion

Apart from strictly following your treatment, you can try out other things to help manage your symptoms. If your symptoms disrupt your day-to-day life, you should talk to your doctor to find out what you can do to better manage your condition.

People with neuroendocrine tumors find it challenging to maintain a healthy weight. So it is important to focus on eating the right foods so that you continue to get proper nutrition. Remember to eat extra protein like eggs, cheese, beans, and fish. If you feel nauseated or you have no appetite, try to eat smaller meals more frequently throughout the day instead of having three big meals in a day. Ginger ale is known to help calm the stomach. At the same time, you should try to avoid having sweets, high-fat foods, and sugary drinks. Junk foods can also aggravate heartburn.

Massage, acupuncture, or yoga can help you relax and manage your symptoms, but you still need to continue your treatment along with these alternative remedies. At the same time, it is always recommended that you check with your doctor before starting any new activities.

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