Pancreatic Neuroendocrine Tumors

Some rare forms of pancreatic cancer form from the abnormal growth of hormone-producing cells in the pancreas called islet cells. These tumors are known as pancreatic neuroendocrine tumors (pancreaticNETs or PNETs), pancreatic endocrine tumors or islet cell tumors.

Islet cells are the endocrine cells in the pancreas that produce and secrete the hormones insulin, glucagon and somatostatin into the bloodstream. Insulin and glucagon are the two main pancreatic hormones. Insulin lowers blood sugar levels while glucagon raises blood sugar levels. Together, these two main hormones work to maintain the proper level of sugar in the blood. Somatostatin regulates the levels of a variety of other hormones in the blood.

Pancreatic neuroendocrine tumors account for less than 5% of all pancreatic tumors. They may be benign or malignant and they tend to grow slower than exocrine tumors. Pancreatic neuroendocrine tumors are either functional (produce hormones) or nonfunctional (produce no hormones). Most functional neuroendocrine tumors are benign. However, 90% of nonfunctional neuroendocrine tumors are cancerous. The following table describes the different types of pancreatic neuroendocrine tumors.

Types Description
Gastrinoma (Zollinger-Ellison Syndrome) Gastrinomas overproduce gastrin. Most are malignant or have the ability to become malignant. When this tumor is inherited as part of a genetic syndrome called Multiple Endocrine Neoplasia Type 1 (MEN1) (see below), multiple tumors may be found in the head of the pancreas and/or the duodenum.

Glucagonomas overproduce glucagon. They are usually large, often metastasize and about 70% are malignant. They are commonly found in the body and tail of the pancreas.

Insulinoma Insulinomas overproduce insulin. They are the most common pancreatic neuroendocrine tumors. They tend to be small and hard to find. Most of them are benign.
Nonfunctional Islet Cell Tumor Nonfunctional islet cell tumors are usually malignant. They are hard to detect.
Somatostatinoma Somatostatinomas overproduce somatostatin. They are extremely rare and usually very large. They can occur anywhere in the pancreas and in the duodenum. They vary in their potential to become malignant.
Vasoactive Intestinal Peptide-Releasing Tumor (VIPoma or Verner-Morrison Syndrome) VIPomas overproduce vasoactive intestinal peptide (VIP). These tumors are usually located in the body and tail of the pancreas. Two-thirds of VIPomas are found in women. The syndrome is also known as Watery Diarrhea and Hypokalemia Achlorhydria (WDHA) Syndrome.

Multiple Endocrine Neoplasia Type-1 (MEN1)
MEN1 (also known as Wermer Syndrome) is a hereditary syndrome that causes multiple tumors in the parathyroid and pituitary glands, and the pancreas. It occurs when tumors are found in at least two of the three endocrine glands mentioned above. About 30-75% of people with MEN1 will develop pancreatic neuroendocrine tumors. Gastrinomas are the most common pancreatic neuroendocrine tumors in individuals with MEN1. The second most common are insulinomas. The tumors in the pancreas may be malignant and generally appear in individuals in their 30’s and 40’s.

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