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Pancreatic Neuroendocrine Tumors: Symptoms and Causes

This article has been medically reviewed by:
Vladimir Neychev, M.D., Ph.D., FACS
Vladimir Neychev, M.D., Ph.D., FACS
Dr. Vladimir Neychev is a board-certified general surgeon and an expert in general, endocrine and endocrine cancer surgery. An M.D./Ph.D./FACS, he is a physician scientist who… Read More
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Most people who receive a diagnosis of a pancreatic neuroendocrine tumor (NET) are hearing of this term for the very first time. If your primary care physician has informed you that you have a pancreatic NET, then you’re probably feeling like you’ve got plenty of research to do. This article will break down the basics of pancreatic neuroendocrine tumors, including what they are, different types, common symptoms and diagnosis. 

What is Pancreatic Neuroendocrine Tumor?

Pancreatic neuroendocrine tumors are found in the pancreas, a large gland located behind the stomach. The pancreas produces digestive fluids that help the body break down food as well as hormones. Pancreatic NETs are rare, accounting for about 25-30 cases per 100,000 people in the United States population. 

Pancreatic NETs don’t typically grow as quickly as some of the more common types of pancreatic cancers. Treatment of patients is usually focused on removing the tumor growth, slowing it down and reducing symptoms. However, every situation is different and treatment will vary from person to person. 

You may also hear of a pancreatic neuroendocrine tumor being referred to as an islet cell tumor. This is because there is a special set of cells in the pancreas called the islet cells. These are the endocrine cells or the cells that release hormones. Pancreatic NETs form in these cells, which is why neuroendocrine tumors of the pancreas are typically referred to as islet cell tumors.

Functional vs. Non-functional Pancreatic NETs

There are two types of pancreatic neuroendocrine tumors, functional and nonfunctional. A functional tumor makes its own hormones and will cause more obvious symptoms than non-functional ones. Non-functional NETs are still cancerous but don’t cause symptoms. 

This means that a non-functional NET is more likely to spread throughout the body without the patient being aware. Typically, patients don’t find out that they have a tumor until it has grown larger and spread throughout the body when it is a non-functional NET. This can make treatment more complicated. 

Two Kinds of Pancreatic Cells

There are two different types of glands in the body: endocrine and exocrine. The pancreas is unique because it has both endocrine and exocrine functions. 

The main difference between exocrine glands and endocrine glands is that exocrine glands secrete substances through a duct while endocrine glands secrete substances directly into the bloodstream. 

Endocrine Pancreas Cells

The endocrine cells of the pancreas are responsible for secreting hormones. The most important hormone secreted by the pancreas is insulin, which helps to regulate the body’s blood sugar. 

The endocrine glands of the pancreas are clustered together in islands, also referred to as islets of Langerhans. Pancreatic NETs develop specifically in the islets of Langerhans in the endocrine cells. 

Exocrine Pancreas Cells

The exocrine component of the pancreas is made up of ducts with small sacs at the end. This part of the pancreas produces specialized proteins or enzymes that enter the GI tract through a duct that connects to the duodenum (the first segment of the small intestine) to help with breaking down fatty foods. 

This is not where pancreatic NETs grow, they are specific to the endocrine cells of the pancreas. 

Types of Pancreatic Neuroendocrine Tumors

There are a few different types of pancreatic neuroendocrine tumors. Typically, pancreatic NETs are broken up into the two categories of “functional” and “nonfunctional.” 

Functional pancreatic NETs can be broken down further into five subtypes: insulinoma, gastrinoma, glucagonoma, VIPoma and somatostatinoma. These subtypes are categorized based on the type of hormones they excrete. 

Functional Pancreatic NETs

Gastrinoma (Zollinger-Ellison Syndrome)

Gastrinomas are a type of pancreatic NET that makes the hormone gastrin. Gastrin is a pancreatic hormone that causes the stomach to produce acid for digestion. Too much gastrin causes excessive release of stomach acid which can lead to severe stomach ulcers, also referred to as Zollinger-Ellison Syndrome. Gastrinomas are rare, occurring in one to two out of one million people per year. 

Glucagonoma

A glucagonoma is a pancreatic NET that secretes the hormone glucagon. Glucagon breaks down glycogen, converting it to glucose and increasing blood sugar levels. For this reason, glucagonomas can cause hyperglycemia or high blood sugar. Glucagonomas are incredibly rare, accounting for only 1% of all neuroendocrine tumors and about 1 case per 20 million people annually. 

Insulinoma

An insulinoma is a type of pancreatic NET that secretes insulin. Insulin is the hormone that is responsible for bringing the blood sugar down when necessary so excess amounts of this hormone can cause hypoglycemia or low blood sugar. Insulinomas are more often noncancerous, about 10% of them become cancerous. Insulinomas occur in about 1-4 people per million in the population. 

Somatostatinoma

A somatostatinoma is a type of pancreatic NET that develops in the head of the pancreas. Somatostatinomas produce a hormone called somatostatin, which stops the production of several other hormones. Somatostatin can affect the production of growth hormone, insulin and gastrin. The annual incidence of somatostatinomas is one in every 40 million. 

VIPoma (Verner-Morrison Syndrome)

Vasoactive intestinal peptide (VIP) is a hormone that helps to move water into the intestines. A VIPoma will begin in the cells of the pancreas and release extra VIP which can cause symptoms such as chronic diarrhea or a syndrome called Verner-Morrison syndrome. 

Non-functional pancreatic NETs and MEN1

Nonfunctional Islet Cell Tumor

A nonfunctional islet cell tumor is another name for a pancreatic NET that does not produce its own hormones. This tumor type is harder to detect since it doesn’t usually cause symptoms.  For this reason, nonfunctional islet cell tumors are usually not detected until they have spread throughout the body or grown. 

Multiple Endocrine Neoplasia Type-1 (MEN1)

MEN1 is a type of condition that sometimes causes pancreatic NETs. MEN1 is hereditary and can cause parathyroid tumors, pancreatic tumors and pituitary tumors. About 1 in every 30,000 people has MEN1.

Symptoms 

Pancreatic NETs sometimes do not cause any symptoms until they have grown and spread throughout the body. Symptoms of a pancreatic NET vary, depending on the subtype it is. Some general symptoms of a pancreatic NET include:

  • Pain in and around the abdomen
  • Yellowing of the skin or eyes also called jaundice 
  • Bloody vomit
  • Abnormal sweating
  • Fast heart rate
  • Anxiety
  • Unexplained weight changes
  • A lump in the abdomen

Here are some symptoms of a pancreatic NET that are specific to the type of NET:

  • Insulinoma: Low blood sugar, fatigue, nervousness, dizziness, lightheadedness, fainting, confusion.
  • Gastrinoma: Diarrhea, stomach ulcers.
  • Glucagonoma: High blood sugar, frequent urination, excessive thirst, extreme hunger, skin rash, blood clots.
  • VIPoma: Watery diarrhea, irregular heartbeat, muscle cramping, decreased reflexes, fatigue, nausea, flushing and redness of the face, neck and chest. 
  • Somatostatinoma: Type 2 diabetes, gallstones, diarrhea, weight loss.

If you’re experiencing strange symptoms, visit a doctor near you so that you can figure out what’s going on.

Diagnosis

There are a variety of different methods that your health care provider can use to confirm your diagnosis of a pancreatic NET. Find below some common diagnostic strategies. 

Background and Clinical Symptoms

Your doctor will evaluate your health history and any symptoms you’ve been experiencing to help with your diagnosis. You’ll be asked about your health, lifestyle, symptoms and family history. Your doctor will also perform a physical exam in which they’ll check your vital signs and look further into any symptoms you’ve reported, such as abdominal pain. 

Laboratory Evaluation

There are a couple of different blood tests your doctor can use to help diagnose your pancreatic tumor, including blood tests, urine tests, biopsies, angiograms and a laparotomy. 

  • Blood Test. Blood tests can help to look for any excessive hormones in the blood that may indicate a functional pancreatic NET. 
  • Urine Test. Urine tests can help to show any broken-down substances that will be excessive in the urine as a result of abnormal hormone release. 
  • Biopsy. A biopsy takes a small sample of tissue from the area of interest (in this case the pancreas) and sends it to a lab to test for abnormal cell growth and other signs of disease. 
  • Angiogram. An angiogram will take an x-ray image of blood vessels surrounding the pancreas to look for cancer cells that have spread around the body. 
  • Laparoscopy. For this diagnostic test, your doctor will use a minimally invasive surgical technique to place a thin tube with a camera on the end into a small incision in your abdomen. This will help them see an up-close look at the cells in your pancreas. 

The endocrinology team at UCF Health is skilled in diagnosing and treating pancreatic neuroendocrine tumors.

Imaging

Your doctor may also want to use imaging tests to get a look at your pancreas to evaluate whether you have a tumor, its size and whether it has spread to other parts of the body. 

  • Intraoperative Ultrasound. An intraoperative ultrasound is an imaging technique that provides high-resolution images of the pancreas. This method is more precise than a standard ultrasound since it is free from interference from surrounding tissues and other bodily structures. 
  • Bone Scan. Bone scans are a type of nuclear imaging that can evaluate how far the cancer has spread. 
  • Endoscopic Ultrasound. An endoscopic ultrasound is a minimally invasive procedure in which you’ll be medicated with a sedative or general anesthesia. Your doctor will place a scope into your mouth that will go through your stomach and small intestine to look at the pancreas more closely. 
  • MRI. An MRI uses radio waves and magnets to help your doctor see if the cancer has spread to other parts of the body, such as the liver. 
  • Abdominal CT Scan. A CT scan takes x-ray images from different angles, combining them to produce detailed images of an organ. 

Treatment 

The treatment approach your doctor takes will vary depending on the type of pancreatic neuroendocrine tumor you have, the size of the tumor and whether it has spread throughout the body. 

Surgery

For pancreatic NETs that haven’t spread beyond the pancreas, surgery is an effective treatment approach. Your doctor will operate on your pancreas to remove the tumor and the portion of the pancreas that is affected. Neuroendocrine tumors of the pancreas may occur in the head or tail of the pancreas. The location will affect the surgical approach your doctor takes. 

Ablation or Embolization

Your doctor may recommend ablation or embolization to treat a pancreatic NET if it has spread to other parts of the body, such as the liver. Ablation destroys tumors with extreme heat or cold. Embolization involves injecting a substance into an artery to block the blood flow to cancer cells so they’ll die. 

Radiation Therapy

Radiation uses radioactive particles to kill cancer cells. Radiation is often used for patients who aren’t able to get surgery for their tumor. Sometimes radiation is given after surgery to help destroy parts of the tumor that weren’t removed. 

Targeted Therapy

Targeted therapy uses drugs that target specific parts of cancer cells and are sometimes used when chemo does not work. When targeted drugs are used for pancreatic NETs, they usually work by blocking the growth of new blood cells that feed cancer or blocking the proteins that help cancer cells grow and survive. 

Chemotherapy

Chemotherapy uses special medications to kill cancer cells. This type of medication may be taken by mouth or through an IV. Treatment with chemotherapy drugs can be useful for cancers that have spread or have not responded to other types of treatment. 

Prevention

There may not be a definitive way to prevent a pancreatic NET since certain factors, such as family history, cannot be controlled. You should always take steps to maintain your overall health,such as smoking and drinking. 

Avoid Smoking

Smoking is a preventable risk factor for pancreatic NETs. Avoid smoking to lower your risk of being diagnosed with one. 

Limit Your Alcohol Intake

It isn’t entirely clear if excessive drinking is a definite risk factor for pancreatic NETs because studies have shown mixed results. 

Life Expectancy

The life expectancy of patients with pancreatic NET will vary greatly depending on the age of the patient, tumor grade, stage of cancer, treatment method and time since diagnosis. The five-year survival rate is used to approximately estimate the chance of survival in patients five years after their diagnosis. For pancreatic NETs, the five-year survival rate is 53%. However, if the pancreatic NET has not spread to other parts of the body and is treatable with surgery, then the five-year survival rate is 74%. 

Conclusion

There is a lot to learn if you’ve recently been diagnosed with a pancreatic neuroendocrine tumor. Pancreatic NETs are often treatable with surgery but the treatment methods vary from patient to patient. Educating yourself is the best way to prepare for cancer treatment so that you can be informed and empowered about all of the treatment options for patients. Schedule an appointment with your doctor at UCF health to figure out a plan today. 

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