Neuroendocrine tumors (NETs) are a type of cancerous growth affecting cells that send hormones around the body. Pancreatic neuroendocrine tumors (PNETs) grow in the cells of the pancreas that produce hormones to control blood sugar.

The pancreas contains two types of cells: endocrine and exocrine. Endocrine cells in the pancreas form clusters of cells called islets that release insulin and glucagon into the blood. These hormones help control blood sugar levels. PNETs start in the islets of the pancreas.

Symptoms of PNETs can vary depending on whether they are functional or nonfunctional. Some symptoms can include weakness, confusion, increased urination, a rapid heart rate, loss of appetite, and more.

Read on to learn about the types, symptoms, and causes of PNETs. This article also looks at diagnosis, treatment options, and more.

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Two types of NETs develop in the pancreas: functional and nonfunctional tumors. Together, they account for less than 2% of all cancers found in the pancreas.

Functional PNETs

Functional PNETs cause the endocrine tissue to make more hormones, including insulin, glucagon, and gastrin.

Different types of functional PNETs can develop based on the hormone they increase, such as:

  • Insulinomas: These are commonly benign, slow-growing tumors that form in cells that produce insulin. Insulin signals to cells across the body that they can take glucose from the blood energy, which helps control blood sugar levels. Insulinomas account for around 70% of functional PNETs.
  • Gastrinomas: These are often cancerous or aggressive tumors that form in gastrin-producing cells. The hormone gastrin triggers the release of stomach acid to digest food. Gastrinomas increase levels of gastrin and stomach acid.
  • Glucagonomas: This typically cancerous tumor forms in cells that produce glucagon. Glucagon makes the liver break down glycogen and release more glucose into the blood. Glucagonomas can lead to higher blood sugar levels.

Nonfunctional PNETs

Nonfunctional PNETs do not make extra hormones or cause signs and symptoms. A person may not experience any symptoms until the tumor grows.

Most nonfunctional PNETs are cancerous.

Learn more about neuroendocrine tumors.

Different types of PNETs cause different symptoms.

Functional PNETs

The symptoms of a functional PNET depend on which hormone levels are increasing.


Insulinomas may cause low blood sugar symptoms, such as:


Glucagonomas can cause symptoms such as:


Gastrinomas can cause symptoms such as:

Nonfunctional PNETs

If a nonfunctional PNET spreads, it can cause symptoms such as:

Cushing syndrome

PNETs can also cause an excess of adrenocorticotropic hormone (ACTH), which can lead to Cushing syndrome.

This can cause a range of symptoms, including:

  • vision loss
  • headache
  • a fatty lump on the back of the neck
  • weight gain in the trunk, face, and neck but thin arms and legs
  • a tendency to bruise easily
  • thin skin
  • purple stretch marks on the abdomen or chest
  • fine hair growth on the face, arms, or upper back
  • slow-healing cuts and sores
  • increased risk of bone fractures
  • irritability
  • anxiety
  • depression

The causes of PNETs are unclear. Around 90% of PNETs are sporadic, meaning they occur randomly.

Cancer occurs due to genetic changes. These changes may switch on genes, called oncogenes, that help cells grow, divide, and die. These changes may also turn off tumor suppressor genes that control cell division or repair damaged DNA.

Certain syndromes related to changes in three tumor suppressor genes may be responsible for inherited cases of PNETs. These syndromes include:

It is also possible to acquire gene changes after birth, sometimes through exposure to chemicals that cause cancer. This may occur through smoking. However, the causes of acquired gene changes are often not clear.

Doctors may start the diagnostic process for PNETs by performing a physical examination and asking about any symptoms the person may be experiencing. The doctor may be able to feel swelling of the liver or gallbladder during the exam.

The doctor can then request tests to confirm the diagnosis, define the type of PNET, and guide treatment.

Tests can include:

  • imaging tests, such as:
    • ultrasound
    • CT scan
    • MRI
    • MR cholangiopancreatography, which produces more detailed images of the pancreas
    • radionuclide scans, which involve passing slightly radioactive substances through the body, which attach to different tumor types
  • blood tests, which can show increased levels of different hormones with links to the islet cells
  • biopsy, which involves removing tissue from the pancreas and examining it under a microscope for PNET cells

Several treatment options can remove, target, and kill PNET cells as well as improve comfort for a person with PNET.


During surgery, the surgeon may remove:

  • the tumor
  • part or all of the pancreas
  • organs to which a PNET may have spread, such as the stomach or liver

A person’s doctor can advise on whether surgery is an option and what the surgery will involve.


Chemotherapy uses one or more cancer drugs to prevent tumors from growing by killing cells or stopping cell division.

Hormone therapy

Hormone therapy removes or blocks hormones that might have links to cancer growth in cancer cells that have hormone receptors. These are places for hormones to attach.

Hepatic arterial occlusion

Hepatic arterial occlusion is a treatment for PNETs that have spread to the liver.

It uses chemicals or other agents to temporarily or permanently block blood flow through the main artery that feeds the liver and kills cancer cells growing there.

Supportive care

Supportive care helps treat symptoms of PNETs. It can include:

  • intravenous (IV) fluids and somatostatin-type drugs to treat diarrhea
  • medications for stomach ulcers
  • insulin medications for high blood sugar

There is no known way to prevent PNETs, according to the American Cancer Society.

However, smoking is a controllable risk factor for PNETs and many other types of pancreatic cancer. Quitting smoking may help reduce the risk for PNETs in people who currently smoke.

The American Cancer Society notes that some studies have also linked heavy alcohol consumption to chronic pancreatitis, which can increase the risk of PNETs. Reducing alcohol use might also reduce the risk of PNETs.

The outlook for a person with PNET depends on many factors, including:

  • the type of PNET
  • the location of the tumor on the pancreas
  • whether the tumor has spread to distant organs
  • whether the person has MEN1 syndrome
  • whether the cancer has returned or if a doctor has diagnosed it for the first time
  • the person’s age and health status

According to the American Cancer Society, the 5-year relative survival rate for PNETs is around 53%. This estimate increases to 95% if the cancer has not spread from the original site, but reduces to 23% if the cancer has reached distant sites.

A relative survival rate helps give an idea of how long a person with a particular condition will live after receiving a diagnosis compared with those without the condition.

For example, if the 5-year relative survival rate is 70%, it means that a person with the condition is 70% as likely to live for 5 years as someone without the condition.

It is important to remember that these figures are estimates. A person can consult a healthcare professional about how their condition is going to affect them.

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Pancreatic neuroendocrine tumors (PNETs) develop in the islet cells of the pancreas. Some types, called functional PNETs, cause symptoms around the body by increasing levels of gastrin, insulin, glucagon, and other hormones. Nonfunctional PNETs do not cause symptoms until the tumor grows or spreads.

The causes of PNETs are unclear but may have links to genetically inherited conditions. A doctor can diagnose a PNET through imaging scans, blood tests, and biopsy.

Treatment includes surgery, chemotherapy, hormone therapy, and hepatic arterial occlusion, as well as symptom management.