Definition of Islet cell cancer

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Islet cell cancer: A rare but highly treatable type of pancreatic cancer that begins in the cells of the pancreas that produce insulin and other hormones. Islet cell cancer can cause the pancreas to produce too much insulin or other hormones. When this happens, the patient may feel weak or dizzy and may have chills, muscle spasms, and diarrhea as well as pain in the stomach or abdomen. Islet cell cancer is also called islet cell carcinoma.

The pancreas has two basic jobs. 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 all pancreatic cancers arise 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.

Islet cell cancers that make hormones are called functioning tumors. Other islet cell cancers do not make hormones and are called nonfunctioning tumors. The majority of functioning tumors that produce insulin are benign. By contrast, 90% of nonfunctioning tumors are malignant. Many islet cell cancers are nonfunctional and produce symptoms from tumor bulk or metastases.

There are several cell types in the pancreatic islet cells (alpha, beta, delta, A, B, C, D, E). The term islet cell carcinoma therefore refers to at least five distinct cancers including gastrinoma, insulinoma, and glucagonoma:

• Gastrinomas -- produce the hormone gastrin and cause the Zollinger-Ellison syndrome of unrelenting peptic ulcers, diarrhea, and gastric hyperacidity.

• Insulinomas -- are characterized by hypoglycemia (low blood sugar) caused by inappropriate secretion of insulin by the tumor. These tumors may occur alone or as part of a MEN (multiple endocrine neoplasia) syndrome.

• Glucagonomas -- produce the hormone glucagon. These are the third most common endocrine-secreting islet cell tumor and 70% of glucagonomas are malignant.