Cancer starts when cells change and grow out of control. The changed (abnormal) cells often grow to form a lump or mass called a tumor. Cancer cells can also grow into (invade) nearby areas. And they can spread to other parts of the body. This is called metastasis.

A pancreatic neuroendocrine tumor is a rare type of cancer that starts in the pancreas. It's often called a pancreatic NET, or a PNET.

The pancreas is an organ that's behind the stomach and in front of the spine. It's a gland that has two main parts:

• The exocrine pancreas. This part makes enzymes that go into the intestines and help break down food.
• The endocrine pancreas. This part makes hormones, like insulin, that are released into the blood.

Most cancers that start in the pancreas are exocrine cancers. Endocrine tumors are much less common and tend to be easier to treat. Endocrine tumors of the pancreas are covered here.

The hormone-making cells of the pancreas bunch together in small clusters all over the pancreas. These clusters are called islets of Langerhans. When a tumor forms in one of these islets, it's called a pancreatic NET. These tumors can be either cancer (malignant) or not cancer (benign). But both types can cause serious health problems.

Pancreatic NETs are grouped based on the hormones they make. The five types are:

• Gastrinoma. Gastrin is a hormone that causes the stomach to make acid to help digest food. A tumor in gastrin-making cells is called a gastrinoma. Most of these tumors are cancer.
• Insulinoma. This tumor starts in the cells that make insulin. Insulin helps control the amount of sugar (glucose) in the blood. Most of these tumors grow slowly and are not cancer.
• Glucagonoma. Glucagon increases the amount of glucose in the blood. A glucagonoma starts in a group of glucagon-making cells. Most of them are cancer.
• VIPoma. These tumors start in cells that make vasoactive intestinal peptide (VIP). VIP controls the balance of water in your body. Most VIPomas are cancer.
• Somatostatinoma. Somatostatin is a hormone that stops the body from making other hormones, like insulin, gastrin, and growth hormone. Most of these tumors are cancer.

These tumors may be called functional NETs because they make hormones. They cause symptoms based on the type of hormone they make. The most common types are gastrinomas and insulinomas.

Nonfunctional pancreatic NETs don't make hormones. They're often quite large when they're found because they don't cause symptoms. They're more likely to be cancer than functional tumors. They're also more common than functional tumors.

These tumors are rare. Experts don't know why people develop them.

A risk factor is anything that may increase your chance of having a disease. The exact cause of someone's cancer may not be known. But risk factors can make it more likely for a person to have cancer.

You are at higher risk for pancreatic NETs if:

• You have certain inherited genetic syndromes (those passed in families), such as:
  • MEN1 (multiple endocrine neoplasia type 1) syndrome.
  • Neurofibromatosis type 1.
  • Von Hippel-Lindau syndrome.
• You drink a lot of alcohol.
• You smoke.
• You have type 2 diabetes.
• You have ongoing inflammation of the pancreas (chronic pancreatitis).

Talk with your doctor about your risk factors for pancreatic NETs and what you can do about them.

Nonfunctioning pancreatic NETs don't cause symptoms until they're big enough to put pressure on other organs, such as the bile ducts.

The symptoms of functional pancreatic NETs depend on what type of tumor you have. This is because the symptoms are caused by the tumor making too much (overproduction) of a hormone.

Here's the breakdown of symptoms that you may have based on tumor type.

These tumors may cause:

• Yellowing of the skin or whites of the eyes (jaundice).
• Diarrhea.
• Indigestion.
• Pain in the belly or back.
• A lump in the belly.
• Weight loss.

Symptoms are caused by too much stomach acid and include:

• Acid reflux.
• Stomach ulcers that keep coming back.
• Pain in the belly or back.
• Diarrhea.

Symptoms are caused by low blood sugar levels and include:

• Blurred vision.
• Weakness.
• Extreme tiredness (fatigue).
• Headache.
• Feeling lightheaded or dizzy.
• Shakiness.
• Irritability.
• Hunger.
• Fast heartbeat.

Symptoms are caused by high blood sugar levels and include:

• Diarrhea.
• Weight loss.
• Mouth dryness.
• Sores at the corner of the mouth or on the tongue.
• Skin rash or dry skin.
• Headaches.
• Feeling very thirsty and hungry.
• Frequent urination.
• Feeling tired, weak, or dizzy.
• Blood clots.

Symptoms include:

• Weight loss.
• Stomach cramps or pain.
• Large amounts of watery diarrhea.
• Flushing (redness) of the face, chest, and neck.
• Dehydration, which can cause dizziness, low urine output, dry skin and mouth, and tiredness.
• Symptoms that are linked to low potassium levels, such as muscle weakness, aches, cramps, numbness, tingling, frequent urination, thirst, and irregular heartbeat (palpitations).

Symptoms include:

• Diarrhea.
• Gallstones.
• Fatty, bad-smelling stools that float.
• Yellowing of the skin or eyes (jaundice).
• Unexplained weight loss.
• High blood sugar symptoms, such as weakness, hunger, confusion, headaches, frequent urination, and dry skin and mouth.

Many of these symptoms may be caused by other health problems. So it's important to see your doctor if you have these symptoms. Only a doctor can tell if you have a tumor or cancer.

If you have any of these symptoms and your doctor thinks you may have a pancreatic NET, you'll be asked about your health history, your symptoms, and your family history. A physical exam will be done.

You may also need one or more of these tests:

• Blood tests and other lab tests. These tests can show high hormone levels in your blood.
• Imaging tests. They are used to look for a tumor inside the pancreas. They include CT scan, PET scan, MRI, ultrasound, and somatostatin receptor scintigraphy.

A biopsy is the only way to know if the tumor is cancer. Small pieces of the tumor are taken out and tested for cancer cells.

After a diagnosis of pancreatic NET, you'll need more tests. They help your doctor learn more about the exact type of cancer. They can help your doctor figure out how fast the cancer is likely to grow and the stage and grade of the cancer.

The stage is how much and how far the cancer has spread (metastasized) in your body. The stage grouping used is a scale of 1 to 4. Roman numerals I (1), II (2), III (3), and IV (4) are used. Stage I tumors are small and only in the pancreas. A stage IV pancreatic NET has spread to other parts of the body. The stage is one of the most important things to know when deciding how to treat the cancer.

The grade is how fast the cancer cells are growing and dividing. It's a scale of 1 to 3 and is based on two things:

• Mitotic index. This is measured by using a microscope to count the number of cells that are dividing.
• Ki-67 index. This is the percentage of cells that are ready to start splitting or dividing.

Once your cancer is staged, your doctor will talk with you about what these details mean for your treatment. Ask your doctor to explain the details of your cancer.

Your treatment choices depend on the type of pancreatic NET you have, your test results, whether the tumor is cancer, and the stage of the cancer. The goal of treatment may be to cure you, to control the tumor or cancer, or to help ease problems caused by the tumor or cancer. Talk with your care team about your treatment choices, the goals of treatment, and what the risks and side effects may be.

Types of treatment for cancer are either local or systemic. Local treatments remove, destroy, or control cancer cells in one area. Surgery and radiation are local treatments. Systemic treatment is used to destroy or control cancer cells that may have traveled around your body. Chemotherapy and targeted therapy, when taken by pill or injection, are systemic treatments. You may have just one treatment or a combination of treatments.

If the tumor can be removed, then surgery is the most common treatment. The type of surgery depends on how big the tumor is and where it is in the pancreas. Nearby tissues, such as parts of the pancreas, stomach, small intestine, or liver may also need to be removed.

For tumors that can't be removed by surgery or tumors that have spread to other parts of the body, other treatments may be used to shrink the tumor, destroy it, or control the symptoms it's causing. These treatments include:

• Watchful waiting (active surveillance), if the tumor is slow-growing and not cancer.
• Chemotherapy.
• Hormone therapy.
• Targeted therapy.
• Using heat to destroy the tumor (radiofrequency ablation).
• Freezing the cancer cells (cryosurgical ablation).

Your doctor uses medicines to help you manage your symptoms from the pancreatic NET. This may include:

• Medicines for stomach ulcers.
• Therapy or over-the-counter remedies to deal with diarrhea.
• Intravenous (I.V.) fluids to help prevent dehydration.
• Medicines or other strategies to keep your blood sugar in a healthy range.

Talk with your doctors about your treatment options. Make a list of questions. Think about the benefits and possible side effects of each option. And talk with your doctor about your concerns before making a decision.

Contact your doctor if you have:

• New symptoms or symptoms that get worse.
• Signs of an infection, such as a fever.

• A pancreatic NET is a tumor that forms in the pancreas.
• These tumors are rare. Experts don't know what causes them.
• Not all pancreatic NETs are cancer.
• Some of these tumors don't cause any symptoms. Others cause symptoms because the tumors make too much of (overproduce) certain hormones.
• Blood tests and imaging scans can help diagnose these tumors.
• Surgery is the main treatment.

Here are some tips to help you get the most from a visit to your doctor.

• Know the reason for your visit and what you want to happen.
• Before your visit, write down questions you want answered.
• Bring someone with you to help you ask questions and remember what your doctor tells you.
• At the visit, write down the name of any new diagnosis and any new medicines, treatments, or tests. Also write down any new directions your provider gives you.
• Know why a new medicine or treatment is prescribed and how it will help you. Also know what the side effects are.
• Ask if your condition can be treated in other ways.
• Know why a test or procedure is recommended and what the results could mean.
• Know what to expect if you do not take the medicine or have the test or procedure.
• If you have a follow-up appointment, write down the date, time, and purpose for that visit.
• Know how you can contact your doctor if you have questions, especially after office hours and on weekends and holidays.