Pancreatic neuroendocrine tumors (otherwise known as islet cell carcinoma or islet cell tumors) are a type of neuroendocrine tumor (NET) found in the pancreas. While a large portion of tumors found in the pancreas are adenocarcinoma (the most common type of pancreatic cancer—accounting for about 90% of all pancreatic cancers), only five percent of pancreatic tumors occur within the islet cells (the hormone-producing cells in the pancreas).
Both benign or malignant, pancreatic neuroendocrine tumors generally advance slower than exocrine tumors, and tend to develop from the abnormal growth of endocrine cells. Some pancreatic neuroendocrine tumors are functional, allowing them to produce excess hormones and therefore leading to a variety of hormone-related issues. By contrast, nonfunctional tumors don’t create hormones.
Widely dependent on the kinds of hormones being produced by the tumor, pancreatic neuroendocrine tumors can cause symptoms ranging from diabetes and gallstones, to ulcers and hypoglycemia, to diarrhea and acromegaly (sudden growth of hands and feet).
There are very few known risk factors for pancreatic neuroendocrine tumors. That said, family histories that feature multiple endocrine neoplasia type 1 (MEN1) syndrome—a rare genetic disorder that can cause the parathyroid glands, pituitary gland, and pancreas to produce too many hormones—may increase the risk for developing pancreatic neuroendocrine tumors.
There are numerous types of functional pancreatic neuroendocrine tumors:
Tumors in the pancreas that produce too much insulin. The pancreas’ job is to make several enzymes and hormones, including insulin (which reduces the level of glucose in the body). Generally speaking, when blood sugar levels drop too low, the pancreas stops making insulin until sugar levels return to normal. However, tumors of the pancreas that produce too much insulin and continue making insulin—even when blood sugars drop—are called insulinomas. Extremely rare, and usually occurring as singly, small tumors in adults, insulinomas are generally non-cancerous (over 90% are benign).
Tumors of the islet cells of the pancreas that interfere with the production of glucose in the blood, causing an increase of blood sugar and diabetes. Glucagonomas is generally malignant (around 60% are cancerous), and tends to spread fairly rapidly. As it directly affects the islet cells of the pancreas, the cells begin making too much glucagon. While genetic factors play a role in some cases
Tumors that disrupt the production of vasoactive intestinal peptide (VIP), which helps control the secretion and absorption of water in the intestines. Also called Verner–Morrison syndrome (after the physicians who first described it) VIPomas are extremely rare (1 per 10,000,000 per year) endocrine tumors, usually causing severe diarrhea.
Tumors that increase the production of gastrin, a stomach acid that helps with digestion and sometimes contributes to stomach ulcers.
Tumors that disrupt the production of a variety of hormones, often leading to diabetes, gallstones, and additional digestive complications.
If symptoms have been reported and a pancreatic neuroendocrine tumor is suspected, doctors will likely request blood and urine samples, to check for abnormal amounts of hormones and/or other substances produced by the tumor. Included in these tests would be screenings for chromogranin A (a protein often seen in many carcinoid tumors), serotonin, and 5HIAA (a byproduct of serotonin). From there, imaging tests would help determine the exact location and size of the tumor, if it has spread to other organs, and whether it can be removed with surgery.