A pancreatic neuroendocrine tumor (PNET) develops in the pancreas from a type of cell known as a neuroendocrine, or an endocrine, cell. These cells manufacture and release hormones such as insulin and glucagon into the bloodstream.

A PNET can be benign (noncancerous) or malignant (cancerous). Certain types of PNETs can cause an overproduction of hormones.

Only 7 percent of pancreatic cancer cases cause PNETs, so these tumors are rare. However, a PNET can result in a variety of symptoms depending on the type of hormone that it produces. If the tumor is malignant and spreads to other parts of the body, the cancer can become very serious.

Other names for a PNET are:

  • neuroendocrine tumor (NET)
  • pancreatic endocrine tumor
  • pancreatic islet cell tumor
  • islet cell tumor
  • islet of Langerhans tumor

PNETs can be either nonfunctional or functional.

Nonfunctional pancreatic neuroendocrine tumors

Nonfunctional pancreatic neuroendocrine tumors produce substances that don’t cause symptoms. The only symptoms are those that result from the growth and spread of the tumor.

These tumors are usually malignant.

Functional pancreatic neuroendocrine tumors

Functional tumors are those that produce a hormone that causes symptoms.

The three main types of functional tumors are insulinomas, gastrinomas, and glucagonomas. Other functional tumors exist, but they’re extremely rare.


An insulinoma is a tumor that produces the hormone insulin. Insulin is responsible for controlling sugar in the bloodstream.

Insulinomas are the most common type of functional PNET, accounting for almost 70 percent of cases. They’re usually benign.


A gastrinoma occurs when the tumor grows from neuroendocrine cells that make the hormone gastrin. Gastrin helps release acid in the stomach for food digestion.

Gastrinomas are usually malignant.


A tumor that produces the hormone glucagon is known as a glucagonoma. This hormone causes the liver to release glucose, or sugar, into the bloodstream.

Glucagonomas are usually malignant.

Rare functional tumors

There are a few types of extremely rare functional PNETs. These include VIPomas, which produce vasoactive intestinal peptide (VIP).

Somatostatinomas are another type. They make the hormone somatostatin, which controls sugar, water, and salt levels in the body.

As with other cancers, stages and substages are used to describe how advanced a PNET is.

The American Joint Committee on Cancer (AJCC) TNM system uses a scale of 1 to 4 for PNETs. It takes into account the following:

  • the size of the tumor (T)
  • whether the tumor’s spread to nearby lymph nodes (N)
  • whether the tumor’s metastasized, or spread, to distant locations (M)

Stage 1

In stage 1, the tumor is no larger than 2 centimeters (.79 inches) across and remains confined to the pancreas.

Stage 2

In some forms of stage 2, the tumor is larger than 2 cm (.79 in) across but is still confined to the pancreas.

You may also be diagnosed with stage 2 if the tumor hasn’t spread to nearby lymph nodes or distant locations, but it has reached the common bile duct or the duodenum. The duodenum is a part of the small intestine.

Stage 3

You’ll be diagnosed with stage 3 if one of the following applies:

  • The tumor has spread to nearby blood vessels or organs (such as the large intestine or spleen), but it hasn’t spread to nearby lymph nodes or distant locations.
  • The tumor has spread to nearby lymph nodes but not to distant locations. The tumor can be any size, and it may or may not be confined to the pancreas.

Stage 4

You’ll be diagnosed with a stage 4 PNET if the tumor has spread to distant locations in the body.

You’ll receive this diagnosis regardless of the tumor’s size, whether it’s confined to the pancreas or not, or whether it’s spread to nearby lymph nodes.

Tumor grades

PNETs are also classified into grades based on how their cells look and whether the cancer is likely to spread.

Grade 1 tumors have normal-looking cells that grow slowly. Grade 3 tumors have abnormal-looking cells that grow quickly. Grade 2 tumors are in the middle. The cells look somewhat abnormal, but they grow more slowly.

The symptoms of a PNET vary depending on the type of tumor.

The symptoms of nonfunctional tumors arise from the growth and spread of the tumor. The symptoms of functional tumors depend on the hormone that’s produced and released into the bloodstream.

Symptoms of a nonfunctional tumor

The symptoms of a nonfunctional tumor include:

  • indigestion
  • increased gas
  • diarrhea
  • abdominal or back pain
  • abdominal mass
  • yellowing of the skin and the whites of the eyes, which is called jaundice or icterus

Symptoms of a gastrinoma

The symptoms of a gastrinoma include:

Symptoms of an insulinoma

An insulinoma can cause an elevated heart rate and low blood sugar. The symptoms of low blood sugar are:

Symptoms of a glucagonoma

The symptoms of a glucagonoma include:

  • a rash on the stomach, legs, or face
  • diarrhea
  • unexplained weight loss
  • tongue and mouth sores

A glucagonoma can also cause a blood clot, which can lead to the following symptoms:

A glucagonoma can also cause high blood sugar, which can lead to these symptoms:

A PNET is a very rare type of tumor. The only known risk factor for developing such a tumor is having a disease called multiple endocrine neoplasia type 1 syndrome (MEN1) or having a family history of the syndrome.

MEN1 is an inheritable disease that causes one or more endocrine glands to be overactive or to grow a tumor. The endocrine glands affected by MEN1 include the pancreas, parathyroid glands, and pituitary gland.

There are several ways your doctor may diagnosis a PNET. The first step is to complete an overall physical exam and a review of your medical and family history. The next step is to either run a blood test or perform an imaging technique to look for a tumor.

Blood tests look for increased levels of hormones and glucose levels in the bloodstream. Increased levels can indicate a PNET.

Imaging tests allow your doctor to visualize your pancreas and look for the presence of a tumor. These tests may include an ultrasound, an MRI, or a CT scan.

Another way to get an image of the pancreas is to perform minor exploratory surgery. Your doctor may want to insert a small camera, or endoscope, into the abdomen to view your pancreas. They could also opt to take a small sample of the tissue for a biopsy.

When a PNET is benign, the treatment may simply involve medications that treat the symptoms of the overproduced hormone. A functional tumor is typically benign. If the symptoms are severe, surgery to remove the tumor may be necessary.

Surgery is the most common treatment for malignant tumors. The purpose of the surgery is to remove as much of the tumor as possible. If the tumor is present in other areas of your body, such as the liver or lungs, your surgeon may remove it from those locations as well.

If the cancer is widespread throughout your body, you may need chemotherapy to decrease the size of the tumors.

The survival rates for people with PNETs are higher than those for people with more common pancreatic cancers.

The statistics below are for people diagnosed between 2009 and 2015 and indicate how many of them live for at least 5 years after diagnosis.

They were taken from the Surveillance, Epidemiology, and End Results (SEER) database, which compiles statistics from multiple regions throughout the United States.

SEER stageEquivalent AJCC stage5-year survival rate
Localized PNETsStage 1, some subtypes of stage 293 percent
Regional PNETsSome subtypes of stage 2, stage 377 percent
Distant PNETsStage 427 percent
All stages combinedAll stages combined54 percent

If your doctor finds a malignant tumor before it spreads beyond the pancreas, the outlook is good. Surgery to remove it usually cures the cancer. The more the cancer cells spread throughout the body, the lower the chances of recovery.

If the tumor is benign, the outlook is also good. Doctors can usually remove the benign tumor and cure the disease through surgery. Medications can relieve symptoms brought about by excess hormones.