Neuroendocrine Tumors


Neuroendocrine tumors (NETs), or sometimes referred to as islet cells, are abnormal growths in the endocrine glands. Since endocrine glands produce hormones, tumors of endocrine glands may also produce hormones. These hormones are often produced in excessive amounts by endocrine tumors and then released into the bloodstream, which can result in profound effects on the body.

Neuroendocrine tumors can be found all over the body. They are most commonly found in the abdomen, and are sometimes further classified as pancreatic neuroendocrine tumors (PNET), when found in the pancreas. PNETs are NETs that arise in the pancreas. They tend to have a slightly worse prognosis in comparison to NETs. Both PNETs and NETs tend to be slow-growing tumors that are treatable even after they have metastasized.

Although NETs are much less common than most GI malignancies, SEER data (from 1973-2004) shows a dramatic 5-fold increase in diagnosed cases. Diagnosed incidence of NETs is predicted to continue rising at a faster rate than most other malignancies.

Neuroendocrine tumors can be benign or malignant. Whether benign or malignant, it is recommended to have all abdominal NETs surgically removed. At the time of resection/following surgery, the distinction of a benign or malignant tumor will be determined.

A way of classifying Neuroendocrine tumors is by the secretion of hormones from the tumor:

  • Non-functioning NETs: Patients with non-functioning tumors do not have any symptoms from excess secretion of pancreatic hormones since the tumor does not secrete any hormones into the blood.
  • Functional NETs: These tumors produce dramatic symptoms because of excess secretion of various different hormones such as insulin, gastrin, or glucagon.


Risk Factors for Neuroendocrine Tumors

Generally, the causes of neuroendocrine tumors are unknown. However, certain types of rare family syndromes have a higher risk of developing NETs, such as:

  • Multiple endocrine neoplasia type 1
  • Neurofibromatosis type 1
  • Von Hippel-Lindau syndrome (VHL)


Symptoms of Neuroendocrine Tumors

Symptoms of neuroendocrine tumors depend on the type of tumor and its location, whether it produces excess hormones, how aggressive it is and whether it has spread to other structures in the body. NETs can be very difficult to diagnose and may take many years to grow to a size larger enough to be seen in imaging scans or produce symptoms.

Up to half of all neuroendocrine tumors produce excess amounts of hormones that produce symptoms in the affected patient. For example, in patients with insulin-producing NETs of the pancreas, excessive insulin decreases blood sugar levels so that symptoms of severe hypoglycemia develop. Whereas, excessive hormones caused by others NETs may cause symptoms such as flushing, diarrhea, asthma and heart valve problems.

Because there are a whole host of unusual symptoms that can be associated with neuroendocrine tumors, it’s important to speak with your physician if you’re experiencing any unusual symptoms, or have a family history of neuroendocrine tumors.

If neuroendocrine tumors are suspected, it’s important to seek proper evaluation and treatment from a healthcare expert experienced in the diagnosis and treatment of gastrointestinal issues.

To schedule a comprehensive diagnostic evaluation, or a second-opinion consultation with a Hoag hepatobiliary and pancreatic expert, visit Meet the Team, or call us at: 949-764-5350.