Pancreatic cancer starts in the cells of the pancreas, an important part of the digestive system. The most common type by far is adenocarcinoma of the pancreas, an exocrine pancreatic cancer in the cells that line the ducts of the pancreas.
Pancreatic cancer: learn more
Five-year pancreatic cancer survival rates
The pancreas sits behind the stomach and is shaped like a fish with a wide head, a tapering body, and a narrow tail. The pancreas is made mostly of exocrine cells. Within the pancreas, exocrine glands make pancreatic enzymes that get released into the intestines via ducts to help you digest food, especially fats.
The most common type of pancreatic cancer is adenocarcinoma of the pancreas. It develops when exocrine cells grow out of control.
Endocrine cells make up a smaller percentage of the cells in the pancreas. These cells make important hormones like insulin and glucagon and release them directly into the blood. Pancreatic neuroendocrine tumors start in the endocrine cells.
Pancreatic cancer is often not detected in its early stages, and it can spread rapidly to other organs. We still don’t know the exact cause of pancreatic cancer, but we do know that some factors increase the risk of developing it.
Types of pancreatic cancer
Exocrine cancers are by far the most common type of pancreas cancer, but there are a few other types as well:
Pancreatic adenocarcinoma. About 95% of cancers of the exocrine pancreas, usually starting in the ducts of the pancreas. Less often, they develop from the cells that make the pancreatic enzymes, in which case they are called acinar cell carcinomas.
Other, less common exocrine cancers include:
- Adenosquamous carcinomas
- Squamous cell carcinomas
- Signet ring cell carcinomas
- Undifferentiated carcinomas
- Undifferentiated carcinomas with giant cells
Ampullary cancer (carcinoma of the ampulla of Vater). This cancer starts in the ampulla of Vater, which is where the bile duct and pancreatic duct come together and empty into the small intestine.
Pancreatic neuroendocrine tumors. These rare tumors start in the endocrine cells.
Benign and precancerous growths
Some growths in the pancreas are not cancer, while others might become cancer over time if left untreated. These are known as precancers.
- Serous cystic neoplasms (SCNs). Tumors that have cysts filled with fluid. SCNs are almost always benign, and most don’t need to be treated unless they grow large or cause symptoms.
- Mucinous cystic neoplasms (MCNs). Slow-growing tumors that have cysts filled with a jelly-like substance called mucin. These tumors almost always occur in women. While they are not cancer, some of them can progress to cancer over time if not treated, so these tumors are typically removed with surgery.
- Intraductal papillary mucinous neoplasms (IPMNs). Benign tumors that grow in the pancreatic ducts. Like MCNs, these tumors make mucin, and over time they sometimes become cancer if not treated.
- Solid pseudopapillary neoplasms (SPNs) are rare, slow-growing tumors that almost always develop in young women. Even though these tumors tend to grow slowly, they can sometimes spread to other parts of the body, so they are best treated with surgery.