What Is Pancreatic Cancer?

In pancreatic cancer, normal cells in the pancreas stop working properly and begin to grow uncontrollably. These cancerous cells can eventually interfere with the proper functioning of the pancreas and metastasize (spread) to other parts of the body.

The pancreas is a digestive organ located toward the back of the abdomen, just below and behind the stomach. It is surrounded by the stomach, small intestine, liver, and spleen. The pancreas produces substances that help break down food into nutrients your body can use for energy. The pancreas also produces insulin, a hormone that regulates the breakdown of food and production of energy.

The American Cancer Society estimates that 43,140 people will be diagnosed with pancreatic cancer in 2010.   It will account for an estimated 3 percent of all new cancer cases. 

The Pancreas and the Digestive System

The pancreas is a gland (an organ that makes substances to help other parts of the body work properly) that lies across your body behind the stomach. It is shaped like a fish with a wide head, a tapering body, and a narrow, pointed tail. The pancreas is about 6 inches long and less than 2 inches wide.

The pancreas has two components:

• Exocrine - The exocrine gland releases pancreatic “juice” into tiny tubes (ducts), which carry the pancreatic juice to the small intestine. This juice contains enzymes, which are proteins that help you digest and break down food, especially fats. Without these enzymes, some of the food you eat would just pass through your intestinal tract and this could lead to diarrhea. More than 95 percent of the cells in the pancreas are exocrine glands and ducts.
• Endocrine - A small percentage of the cells in the pancreas are endocrine cells. These cells are arranged in small clusters (islets of Langerhans). The islets release two hormones (chemicals that control the actions of certain cells organs): insulin, which reduces the amount of sugar in the blood, and glucagon, which increases the amount of sugar in the blood. A defect in insulin production can result in diabetes.

The pancreas plays a major role in your digestive system. After you eat, your esophagus carries the food from your mouth to your stomach. This tube goes down from the mouth and through an opening in the diaphragm, which is a dome-shaped muscle that separates the lungs and heart from the abdomen and helps you breathe.

Your esophagus empties into your stomach. The stomach muscles mix the food with acids and enzymes, breaking it into much smaller, more digestible pieces. From the stomach, the food flows directly into the duodenum, which is the first part of the small intestine’s three parts:

• The duodenum - The c-shaped first part
• The jejunum - The coiled midsection
• The ileum - The final section that leads into the large intestine

The pancreas makes enzymes that help digest proteins, fats, and carbohydrates. It also makes a substance that neutralizes stomach acid. The liver produces bile, a greenish-yellow fluid that helps the body digest fat. After the liver cells make the bile, it travels down through the bile ducts, which merge with the cystic duct to form the common bile duct. The cystic duct goes into the gallbladder, a small pouch that stores extra bile until it is needed. The common bile duct goes into the head of the pancreas and joins the pancreatic duct to form the ampulla of Vater, which then empties into the duodenum.

From the small intestine, undigested food, bile, and pancreatic fluid travel to the large intestine. The large intestine's main job is to remove water from the undigested food and form solid waste that can be passed out of the body.

How Pancreatic Cancer Starts

Most pancreatic cancers begin in the ducts that carry pancreatic juices. When pancreatic cancer spreads (metastasizes) outside the pancreas, cancer cells often travel to nearby lymph nodes (tiny organs throughout the body that are shaped like beans and help fight infections). Once the cancer reaches these nodes, it may also spread to other lymph nodes or other tissues, such as the liver or lungs. Sometimes pancreatic cancer spreads to the peritoneum, the tissue that lines the abdomen.

When cancer spreads from its original place to another part of the body, the new tumor has the same kind of abnormal cells and the same name as the primary tumor. For example, if pancreatic cancer spreads to the liver, the cancer cells in the liver are pancreatic cancer cells. The disease is metastatic pancreatic cancer, not liver cancer, and it is treated as pancreatic cancer.

Types of Pancreatic Cancer

Doctors classify pancreatic cancers into two main types—exocrine and endocrine—depending on the type of cells in which the tumor starts.

Most pancreatic cancers (about 95 percent of all cases) start in the exocrine gland or the ampulla of Vater in the pancreas. The exocrine gland releases pancreatic “juice” into tiny tubes (ducts). The ducts carry the pancreatic juice to the small intestine. This juice contains enzymes that help digest and break down food, especially fats. The ampulla of Vater is the place where the pancreatic duct enters the duodenum, the part of the small intestine that is connected to the stomach. 

Only about 5 percent of all pancreatic cancers start in the endocrine cells of the pancreas. These cells are arranged in small clusters (islets of Langerhans). The islets produce insulin, which reduces the amount of sugar in the blood, and glucagon, which increases the amount of sugar in the blood. A defect in insulin production can result in diabetes.

Exocrine and endocrine cancers of the pancreas have different risk factors, causes, and signs and symptoms. They are also diagnosed using different tests and treated in different ways. Because these cancers are so different, the information in this pancreatic cancer site pertains only to exocrine pancreatic and ampullary cancers, which account for the vast majority of pancreatic cancers.

Ampullary Tumors

• Ampullary cancer (also known as carcinoma of the ampulla of Vater) - These tumors can develop where the bile duct and pancreatic duct come together and empty into the duodenum. Because ampullary cancers develop very close to the common bile duct, they often block the bile duct while they are still small and have not spread far. For this reason, ampullary cancers are usually diagnosed at an earlier stage than most pancreatic cancers, making them easier to treat successfully.

Exocrine Tumors

• Adenocarcinoma - Adenocarcinomas usually begin in the ducts of the pancreas but sometimes start in the cells that produce the pancreatic enzymes (acinar cell carcinomas). Adenocarcinomas account for 75 percent of all pancreatic cancers. They often spread (metastasize) to the liver or lymph nodes.

Other, much less common exocrine tumors of the pancreas include:

• Acinar cell carcinoma - This rare cancerous tumor also secretes digestive enzymes.
• Adenosquamous carcinoma - This type of tumor is similar to adenocarcinoma, but also has another cell type called squamous cells.
• Giant cell tumor - Giant cell tumors are extremely rare and grow less quickly than adenocarcinoma. They have unusually large cells, but these tumors are the same size as other pancreatic tumors.
• Intraductal papillary-mucinous neoplasm - These tumors start in the pancreatic duct or branches of the duct. The tumors look like fingerlike projections into the duct.
• Mucinous cystadenocarcinoma - These spongy tumors are filled with a thick fluid (mucin).
• Pancreatoblastoma - Pancreatoblastomas are more common in children under the age of 10.
• Solid and pseudopapillary tumor - These tumors can start anywhere in the pancreas. Some parts of the tumor are solid, while other parts are papillary (with fingerlike projections). These tumors occur mostly in women in their 30s.

Endocrine (Islet Cell) Tumors

Cancers of the endocrine pancreas are highly treatable, often curable, and rare. Only 200 to 1,000 people are diagnosed with these cancers each year in the United States. Because these tumors are diagnosed and treated very differently from the much more common adenocarcinomas of the exocrine pancreas, the remainder of this site does not discuss cancers of the endocrine pancreas.

• Insulinoma - Insulinomas produce too much insulin and are the most common endocrine cancers of the pancreas. Only 5 percent to 10 percent of insulinomas are cancerous.
• Gastrinoma (Zollinger-Ellison syndrome) - Gastrinomas cause the stomach to secrete excess gastric juices. More than 60 percent of gastrinomas are cancerous and the tumor eventually spreads to the liver and other parts of the body.
• Glucagonoma - Glucagonoma is a rare pancreatic tumor that produces too much glucagon, a hormone that increases the amount of sugar in the blood. Glucagonomas can produce symptoms similar to diabetes.
• Nonfunctioning islet cell tumors - These tumors do not have the same types of symptoms as the other endocrine tumors. As a result, they are usually diagnosed at more advanced stages of disease.
• Somatostatinomas - These tumors are usually found in the pancreas, but they can also start in other parts of the intestinal tract. Somatostatinoma sometimes make somatostatin, a hormone that stops the pancreas from making several other hormones (such as growth hormone, insulin, and gastrin).
• Vasoactive intestinal peptide-producing tumor (VIPoma or Verner-Morrison syndrome) - VIPomas affect cells in the pancreas that produce vasoactive intestinal peptide (VIP), a hormone that helps carry water in the intestines. Too much VIP can cause chronic, watery diarrhea.

Key Statistics

Pancreatic cancer will be the tenth most commonly diagnosed form of cancer among men in United States in 2010, according to estimates from the American Cancer Society. Over the past 15 to 25 years, rates of pancreatic cancer have slowly dropped in both men and women.

This content has been reviewed and approved by Myo Thant, MD.