What are islet cell tumors?

What are islet cell tumors?

An islet cell tumor is a mass of abnormal cells that forms in the endocrine (hormone -producing) tissues of the pancreas. Islet cell tumors may be benign (noncancer) or malignant (cancerous). Islet cell cancer is rare.

The pancreas is about 6 inches long and is shaped like a thin pear, wider at one end and narrower at the other. The pancreas lies behind the stomach, inside a loop formed by part of the small intestine. The broader right end of the pancreas is called the head, the middle section is called the body, and the narrow left end is the tail.

The pancreas has two basic jobs in the body. It produces digestive juices that help break down (digest) food, and hormones (such as insulin) that regulate how the body stores and uses food. The area of the pancreas that produces digestive juices is called the exocrine pancreas. About 95% of pancreatic cancers begin in the exocrine pancreas. The hormone-producing area of the pancreas has special cells called islet cells and is called the endocrine pancreas. Only about 5% of pancreatic cancers start here. This summary has information on cancer of the endocrine pancreas (islet cell cancer). (See the PDQ summary on Pancreatic Cancer Treatment ¹ for more information on cancer of the exocrine pancreas.)

The islet cells in the pancreas make many hormones, including insulin, which help the body store and use sugars. When islet cells in the pancreas become cancerous, they may make too many hormones. Islet cell cancers that make too many hormones are called functioning tumors. Other islet cell cancers may not make extra hormones and are called nonfunctioning tumors. Tumors that do not spread to other parts of the body can also be found in the islet cells. These are called benign tumors and are not cancer. A doctor will need to determine whether the tumor is cancer or a benign tumor.

A doctor should be seen if there is pain in the abdomen, diarrhea, stomach pain, a tired feeling all the time, fainting, or weight gain without eating too much.

If there are symptoms, the doctor will order blood and urine tests to see whether the amounts of hormones in the body are normal. Other tests, including x-rays and special scans, may also be done.

The chance of recovery (prognosis) depends on the type of islet cell cancer the patient has, how far the cancer has spread, and the patient’s overall health.

Glossary Terms

The area of the body that contains the pancreas, stomach, intestines, liver, gallbladder, and other organs.

Not normal. An abnormal lesion or growth may be cancer, premalignant (likely to become cancer), or benign (not cancer).

Not cancer. Benign tumors may grow larger but do not spread to other parts of the body.

A tissue with red blood cells, white blood cells, platelets, and other substances suspended in fluid called plasma. Blood takes oxygen and nutrients to the tissues, and carries away wastes.

A term for diseases in which abnormal cells divide without control and can invade nearby tissues. Cancer cells can also spread to other parts of the body through the blood and lymph systems. There are several main types of cancer. Carcinoma is cancer that begins in the skin or in tissues that line or cover internal organs. Sarcoma is cancer that begins in bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue. Leukemia is cancer that starts in blood-forming tissue such as the bone marrow, and causes large numbers of abnormal blood cells to be produced and enter the blood. Lymphoma and multiple myeloma are cancers that begin in the cells of the immune system. Central nervous system cancers are cancers that begin in the tissues of the brain and spinal cord.

The individual unit that makes up the tissues of the body. All living things are made up of one or more cells.

Frequent and watery bowel movements.

Refers to tissue that makes and releases hormones that travel in the bloodstream and control the actions of other cells or organs. Some examples of endocrine tissues are the pituitary, thyroid, and adrenal glands.

A pancreatic cell that produces hormones (e.g., insulin and glucagon) that are secreted into the bloodstream. These hormones help control the level of glucose (sugar) in the blood. Also called islet cell and islet of Langerhans cell.

A pancreatic cell that produces enzymes that are secreted into the small intestine. These enzymes help digest food as it passes through the gastrointestinal tract.

A tumor that is found in endocrine tissue and makes hormones (chemicals that travel in the bloodstream and control the actions of other cells or organs).

One of many chemicals made by glands in the body. Hormones circulate in the bloodstream and control the actions of certain cells or organs. Some hormones can also be made in the laboratory.

A hormone made by the islet cells of the pancreas. Insulin controls the amount of sugar in the blood by moving it into the cells, where it can be used by the body for energy.

A pancreatic cell that produces hormones (e.g., insulin and glucagon) that are secreted into the bloodstream. These hormones help control the level of glucose (sugar) in the blood. Also called endocrine pancreas cell and islet of Langerhans cell.

A rare cancer that forms in the islets of Langerhans cells (a type of cell found in the pancreas). Also called pancreatic endocrine cancer.

Cancerous. Malignant tumors can invade and destroy nearby tissue and spread to other parts of the body.

A tumor that is found in endocrine tissue but that does not make extra hormones (chemicals that travel in the blood and control the actions of other cells or organs).

A glandular organ located in the abdomen. It makes pancreatic juices, which contain enzymes that aid in digestion, and it produces several hormones, including insulin. The pancreas is surrounded by the stomach, intestines, and other organs.

A disease in which malignant (cancer) cells are found in the tissues of the pancreas. Also called exocrine cancer.

PDQ is an online database developed and maintained by the National Cancer Institute. Designed to make the most current, credible, and accurate cancer information available to health professionals and the public, PDQ contains peer-reviewed summaries on cancer treatment, screening, prevention, genetics, complementary and alternative medicine, and supportive care; a registry of cancer clinical trials from around the world; and directories of physicians, professionals who provide genetics services, and organizations that provide cancer care. Most of this information, and more specific information about PDQ, can be found on the NCI's Web site at http://www.cancer.gov/cancertopics/pdq. Also called Physician Data Query.

The likely outcome or course of a disease; the chance of recovery or recurrence.

A picture of structures inside the body. Scans often used in diagnosing, staging, and monitoring disease include liver scans, bone scans, and computed tomography (CT) or computerized axial tomography (CAT) scans and magnetic resonance imaging (MRI) scans. In liver scanning and bone scanning, radioactive substances that are injected into the bloodstream collect in these organs. A scanner that detects the radiation is used to create pictures. In CT scanning, an x-ray machine linked to a computer is used to produce detailed pictures of organs inside the body. MRI scans use a large magnet connected to a computer to create pictures of areas inside the body.

The part of the digestive tract that is located between the stomach and the large intestine.

An organ that is part of the digestive system. The stomach helps digest food by mixing it with digestive juices and churning it into a thin liquid.

An indication that a person has a condition or disease. Some examples of symptoms are headache, fever, fatigue, nausea, vomiting, and pain.

A group or layer of cells that work together to perform a specific function.

An abnormal mass of tissue that results when cells divide more than they should or do not die when they should. Tumors may be benign (not cancer), or malignant (cancer). Also called neoplasm.

Fluid containing water and waste products. Urine is made by the kidneys, stored in the bladder, and leaves the body through the urethra.

A type of high-energy radiation. In low doses, x-rays are used to diagnose diseases by making pictures of the inside of the body. In high doses, x-rays are used to treat cancer.