Islet Cell Tumors (Endocrine 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.

The endocrine portion of the pancreas takes the form of many small clusters of cells called islets of Langerhans or, more simply, islets. Humans have roughly one million islets. In standard histological sections of the pancreas, islets are seen as relatively pale-staining groups of cells embedded in a sea of darker-staining exocrine tissue. The image to the right shows three islets in the pancreas of a horse.

The pancreas, named for the Greek words pan (all) and kreas (flesh), is a 12-15 – cm long J-shaped (like a hockey stick), soft, lobulated, retroperitoneal organ. It lies transversely, although a bit obliquely, on the posterior abdominal wall behind the stomach, across the lumbar (L1-2) 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. Malignant islet cell tumors are a rare type of pancreatic cancer.
• 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.

An islet cell tumor may also be called a pancreatic endocrine tumor (PET), pancreatic neuroendocrine tumor, islet cell carcinoma, or pancreatic carcinoid.

Islet cell tumors may or may not cause symptoms

Islet cells make and release hormones into the blood. Islet cell tumors may be functional (the hormones that are released cause symptoms) or nonfunctional (the hormones that are released do not cause symptoms) tumors:

* Functional tumors make one or more hormones, such as gastrin, insulin, and glucagon, that cause symptoms. Most functional tumors are benign (not cancer).
* Nonfunctional tumors make hormones that do not cause symptoms. Symptoms are caused by the tumor as it spreads and grows. Most nonfunctional tumors are malignant (cancer).

There are different kinds of functional islet cell tumors

Islet cells make different kinds of hormones such as gastrin, insulin, and glucagon. Types of functional islet cell tumors include the following: