What is pancreatic cancer?
To understand pancreatic cancer, it helps to know about the pancreas and what it does.
The normal pancreas
The pancreas is an organ deep in the body, behind the stomach. It is shaped a little like a fish. In adults it is about 6 inches long and less than 2 inches wide. It goes across the belly (abdomen).
The pancreas has 2 different kinds of glands.
- The exocrine glands make pancreatic “juice,” which goes into the intestines. This juice has enzymes that break down the foods you eat so the body can use them. Most of the cells in the pancreas are part of the exocrine system.
- A smaller number of cells in the pancreas are endocrine cells. These cells are in clusters called islets. They make hormones like insulin that help balance the amount of sugar in the blood.
Benign pancreatic tumors and precancers
Not all of the tumors in the pancreas are cancer. Some tumors are not cancer (they are benign), while others might become cancer over time if left untreated. (These are known as precancers.) Examples of these tumors include:
- Serous cystic neoplasms (SCNs)
- Mucinous cystic neoplasms (MCNs)
- Intraductal papillary mucinous neoplasms (IPMNs)
To learn more about these tumors, see our document Pancreatic Cancer.
Cancer starts when cells in the body begin to grow out of control. Cells in nearly any part of the body can become cancer, and can spread to other areas of the body. To learn more about how cancers start and spread, see What Is Cancer?
Both the exocrine and endocrine cells of the pancreas can form cancers. But cancers formed by the exocrine cells are much more common. When someone says that they have pancreatic cancer, they usually mean an exocrine pancreatic cancer.
It is important to know whether a tumor is from the exocrine or endocrine part of the pancreas. These tumors have their own signs and symptoms, are found using different tests, are treated in different ways, and have different outlooks.
Exocrine tumors are by far the most common type of pancreas cancer. Nearly all of these tumors are adenocarcinomas (cancers that start in gland cells).
A special type of cancer (called ampullary cancer) starts where the bile duct (from the liver) and the pancreatic duct empty into the small intestine (called the ampulla of Vater –see the drawing above). This type of cancer often causes symptoms while it is still small, so it is usually found at an earlier stage than most pancreatic cancers. Finding it early means that the chances of successful treatment are better.
Tumors of the endocrine pancreas are much less common. They are known as islet cell tumors or neuroendocrine tumors. There are many types, including:
Most of these tumors are not cancer (benign), but there are a few that are cancer. The outlook for these tumors is usually better than that of pancreatic exocrine cancers.
This information covers only exocrine cancer and ampullary cancer. Please see Pancreatic Cancer to learn more about neuroendocrine tumors of the pancreas.
Last Medical Review: 08/01/2014
Last Revised: 02/01/2016