Islet cell tumors


Islet cell tumors, also called pancreatic neuroendocrine tumors (pNETs), are a diverse group of rare pancreatic lesions that make up about 5% of pancreatic tumors. The tumors grow slowly and develop within islet cells, the endocrine cells of the pancreas that produce hormones such as insulin, which regulates blood sugar.

Pancreatic neuroendocrine tumors are different from pancreatic adenocarcinomas, which make up 95% of all pancreatic tumors and develop from the exocrine tissue of the pancreas Adenocarcinomas have different risk factors and causes, distinct signs and symptoms, and are treated in different ways with different prognoses.

While they are less common than pancreatic adenocarcinomas, islet cell tumors have a better prognosis. However, they can be more difficult to detect and may have symptoms that don’t specifically point to islet cell tumors.

Islet cell tumors are classified as functional or nonfunctional. If they produce excessive hormones that result in clinical symptoms, they are classified as functional. Otherwise, they are classified as non-functional.

The three most common functional islet cell tumors include gastrinoma, insulinoma, and glucagonoma, all of which correspond to the different types of cells in which the tumor forms. The two types of rare functional islet cell tumors are called VIPomas and somatostatinomas. The methods for diagnosing these types of tumors can be different. 

Our approach

Under the supervision of Dr. Gene Coppa, Chairman of Surgery, the Northwell Health’s Pancreas Disease Center has extensive experience in the surgical treatment of islet cell tumors. Our skilled staff of surgeons, gastroenterologists, endocrinologists, and nurse practitioners are dedicated to setting you on a path of health and wellness through innovative treatments and customized care.

We understand that diseases of the pancreas can be difficult to diagnose and treat. The wide range of symptoms and risk factors require careful testing and examination. We’ll guide you through the process, step-by-step -- and once we make a thorough diagnosis, we’ll work with you to create a care plan with the best treatment options for you. Learn more about the Pancreas Disease Center and how we can help create a better life for you.

Signs and symptoms

Functional tumors generally over-produce different hormones, which in turn produce different symptoms.

Insulinoma form in the cells that make insulin and are seen in about 35-40% of pNET cases.  Symptoms generally include low blood sugar, dizziness, light headedness, weakness, confusion, tremors, and visual changes.  The malignancy rate is about 5-10%.

Gastrinoma (Zoller-Ellision syndrome) form in the cells that make gastrin and make up about 15-35% of pNETs.  They are characterized by abdominal pain, diarrhea, peptic ulcer disease.  The malignancy rate is about 40–60%.

Glucagonoma forms in the cells that make glucagon and represent less than 10% of pNETs. Commons symptoms of this tumor are skin rash (Necrolytic migratory necrolytic erythema), diabetes, diarrhea, deep vein thrombosis (DVT).   Malignancy rates are 60-80%.

VIPomas (Verne-Morrison) are known to cause severe diarrhea (stools can be tea colored and odorless), dehydration, muscle weakness, hypokalemia (potassium deficiency in the bloodstream), achlorhydria. These tumors are rare and make up < 10% of pNETs, with 60-70%, malignant.

Somatostatinoma symptoms include weight loss, anemia, foul smelling and oily stools (steatorrhea), diabetes, and gallbladder disease.  These tumors represent the rarest of the pancreatic neuroendocrine tumor at less than 5%.  About 50-70% of these tumors are malignant.

Non-functional tumors are often quite advanced when they are discovered because they do not initially produce signs or symptoms. 

Risk factors

The primary known risk factor for developing an islet cell tumor is a rare genetic condition called Multiple Endocrine Neoplasia 1 (MEN 1), which causes an overproduction of parathyroid, pituitary gland, and pancreatic hormones. 


At the Pancreas Disease Center, we use the following tests to detect and diagnose islet cell tumors:

Physical Exam

The first step is to complete a comprehensive physical exam and review the patient’s medical and family history.


  • Blood and urine tests are performed to look for increased levels of hormones and other substances.
  • Molecular testing is used to identify genes, proteins and other factors unique to the tumor.


Localization and tumor staging is essential for the appropriate diagnosis and treatment of neuroendocrine tumors. Computed tomography (CT), magnetic resonance imaging (MRI), somatostatin receptor scintigraphy (SRS), positron-emission tomography (PET), and endoscopic ultrasonography (EUS) are used to visualize and look for the presence of the tumor. In cases when the tumor cannot be located with these tools, an angiography with selective arterial stimulation and venous sampling is used.


A biopsy may be performed to confirm the diagnosis.



Surgery is the preferred method of treatment; the type of surgical procedure chosen is dependent on the tumor’s location and size.

  • A whipple procedure is performed for tumors located in the head of the pancreas.  This surgery involves the removal of parts of the pancreas, small intestine, and gallbladder.
  • A distal pancreatectomy is usually indicated if the tumor is found in the tail of the pancreas.
  • Enucleation of pancreatic islet cell tumors can be performed on insulinomas and gastrinomas, which are typically less than 1 to 2 cms. The tumors are often on the surface of the pancreas so the tumor can be excised from the pancreas without removing pancreatic tissue.

Neuroendocrine tumors can be removed using minimally-invasive, laparoscopic or robotic surgery. Open surgery is normally performed if:

  • The tumor is large (10 cms)
  • There is presence of metastases
  • There is invasion of the tumor into the major blood vessels around the pancreas

Medical Therapy
Pancreatic neuroendocrine tumors grow slowly and generally do not respond well to conventional chemotherapy, which targets rapidly growing cells. However, the U.S. Food and Drug Administration (FDA) recently approved medication for the treatment of advanced pancreatic neuroendocrine tumors.  The Pancreas Disease Center physicians can discuss these options with you. 


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