Pancreatic Neuroendocrine Tumors (Islet Cell Tumors) Treatment (PDQ®): Treatment - Patient Information [NCI]-General Information About Pancreatic Neuroendocrine Tumors (Islet Cell Tumors) Pancreatic neuroendocrine tumors form in hormone-making cells (islet cells) of the pancreas.

The pancreas is a gland about 6 inches long that is shaped like a thin pear lying on its side. The wider end of the pancreas is called the head, the middle section is called the body, and the narrow end is called the tail. The pancreas lies behind the stomach and in front of the spine.

Anatomy of the pancreas. The pancreas has three areas: head, body, and tail. It is found in the abdomen near the stomach, intestines, and other organs.

There are two kinds of cells in the pancreas:

• Endocrine pancreas cells make several kinds of hormones (chemicals that control the actions of certain cells or organs in the body), such as insulin to control blood sugar. They cluster together in many small groups (islets) throughout the pancreas. Endocrine pancreas cells are also called islet cells or islets of Langerhans. Tumors that form in islet cells are called islet cell tumors, pancreatic endocrine tumors, or pancreatic neuroendocrine tumors (pancreatic NETs).
• Exocrine pancreas cells make enzymes that are released into the small intestine to help the body digest food. Most of the pancreas is made of ducts with small sacs at the end of the ducts, which are lined with exocrine cells.

This summary discusses islet cell tumors of the endocrine pancreas. See the PDQ summary on Pancreatic Cancer Treatment for information on exocrine pancreatic cancer.

Pancreatic neuroendocrine tumors (NETs) may be benign (not cancer) or malignant (cancer). When pancreatic NETs are malignant, they are called pancreatic endocrine cancer or islet cell carcinoma.

Pancreatic NETs are much less common than pancreatic exocrine tumors and have a better prognosis.

Pancreatic NETs may or may not cause signs or symptoms.

Pancreatic NETs may be functional or nonfunctional:

• Functional tumors make extra amounts of hormones, such as gastrin, insulin, and glucagon, that cause signs and symptoms.
• Nonfunctional tumors do not make extra amounts of hormones. Signs and symptoms are caused by the tumor as it spreads and grows. Most nonfunctional tumors are malignant (cancer).

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