user: What is (are) Pancreatic Neuroendocrine Tumors (Islet Cell Tumors) ?

assistant: Key Points
                    - Pancreatic neuroendocrine tumors form in hormone-making cells (islet cells) of the pancreas.    - Pancreatic NETs may or may not cause signs or symptoms.    - There are different kinds of functional pancreatic NETs.     - Having certain syndromes can increase the risk of pancreatic NETs.     - Different types of pancreatic NETs have different signs and symptoms.     - Lab tests and imaging tests are used to detect (find) and diagnose pancreatic NETs.     - Other kinds of lab tests are used to check for the specific type of pancreatic NETs.    - Certain factors affect prognosis (chance of recovery) and treatment options.
                
                
                    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.      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.
                
                
                    There are different kinds of functional pancreatic NETs.
                    Pancreatic NETs make different kinds of hormones such as gastrin, insulin, and glucagon. Functional pancreatic NETs include the following:         -   Gastrinoma: A tumor that forms in cells that make gastrin. Gastrin is a hormone that causes the stomach to release an acid that helps digest food. Both gastrin and stomach acid are increased by gastrinomas. When increased stomach acid, stomach ulcers, and diarrhea are caused by a tumor that makes gastrin, it is called Zollinger-Ellison syndrome. A gastrinoma usually forms in the head of the pancreas and sometimes forms in the small intestine. Most gastrinomas are malignant (cancer).    -   Insulinoma: A tumor that forms in cells that make insulin. Insulin is a hormone that controls the amount of glucose (sugar) in the blood. It moves glucose into the cells, where it can be used by the body for energy. Insulinomas are usually slow-growing tumors that rarely spread. An insulinoma forms in the head, body, or tail of the pancreas. Insulinomas are usually benign (not cancer).    -   Glucagonoma: A tumor that forms in cells that make glucagon. Glucagon is a hormone that increases the amount of glucose in the blood. It causes the liver to break down glycogen. Too much glucagon causes hyperglycemia (high blood sugar). A glucagonoma usually forms in the tail of the pancreas. Most glucagonomas are malignant (cancer).    -  Other types of tumors: There are other rare types of functional pancreatic NETs that make hormones, including hormones that control the balance of sugar, salt, and water in the body. These tumors include:                - VIPomas, which make vasoactive intestinal peptide. VIPoma may also be called Verner-Morrison syndrome.      - Somatostatinomas, which make somatostatin.         These other types of tumors are grouped together because they are treated in much the same way.