What is the Pancreas?

The pancreas measures approximately 6 inches long and is shaped like a thin, flat pear, although physicians are taught to consider the pancreas like a fish with a head, body and tail. Centrally located deep within the upper abdomen, the pancreas is surrounded by the stomach, liver, intestines, colon, and other organs. The pancreas has two primary functions: to produce enzymes that assist the body with the digestion of fats and proteins, and to produce hormones, such as insulin and glucagon, that perform a variety of body functions such as regulating how much sugar is present in the blood.

Islet Cell Tumors

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Types of Pancreatic Tumors

The most common types of pancreatic tumors include:

  • An adenocarcinoma is a malignant tumor that arises from the pancreatic ductal epithelium, or the lining of the pancreatic ducts. Approximately 95% of all tumors of the pancreas are adenocarcinomas. These tumors most often form at the head of the pancreas but can also develop within the body or tail of the organ.
  • Islet cell tumors are another, much rarer, type of pancreatic tumor that make up about 5% of all diagnoses. Unlike adenocarcinomas, islet cell tumors may be benign or malignant. Islet cell tumors arise from the endocrine cells of the pancreas, the cells responsible for the production of insulin and other hormones. These endocrine cells form small clusters in the pancreas called the islets of Langerhans.

The rest of this page will focus primarily on the islet cell tumors found in the endocrine glands of the pancreas.

Pancreatic Islet

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Types of Islet Cell Tumors

Functioning: Functioning islet cell tumors overproduce one or more of a variety of hormones and are associated with specific symptoms depending on the hormone(s) produced. These hormones may include:

  • Insulin - Insulin is a hormone that regulates the level of glucose in the blood. Tumors that form in insulin-producing cells are called insulinomas. These tumors are most often benign and slow-growing.
  • Gastrin - Gastrin is a hormone that causes the stomach to secrete acid to help digest food. Tumors that form in gastrin-producing cells are called gastrinomas. Gastrinomas are usually malignant.
  • Glucagon - Glucagon is a hormone that increases the amount of glucose in the blood. Tumors that form in glucagon-producing cells are called glucagonomas. Glucagonomas are very rare and are usually malignant.
  • Vasoactive intestinal peptide (VIP) - VIP is a hormone that helps secrete water and electrolytes into the digestive system and relaxes the muscles in the digestive system. VIP is also involved in many other systems in the body. Tumors that overproduce VIP and are associated with certain symptoms are called VIPomas and are extremely rare.
  • Somatostatin - Somatostatin is a hormone that regulates the levels of other hormones throughout the body. Tumors that form in these cells are called somatostatinomas and are very rare. These tumors can disrupt the levels of other hormones throughout the body.

Non-functioning: Non-functioning islet cell tumors are not associated with symptoms caused by excess hormone production. Symptoms of non-functioning tumors are caused only by the tumor growing and spreading, but most non-functioning tumors are found incidentally, without symptoms, or on imaging tests for unrelated symptoms. Both functioning and non-functioning islet cell tumors can behave in either a benign or malignant fashion.