Your pancreas is about 6 inches long and looks something like a pear lying on its side. The wider end (head) is located near the center of your abdomen next to the upper part of your small intestine (duodenum). The main part (body) of the pancreas stretches behind your stomach, and the narrow end (tail) is on your left side, next to your spleen.
A part of your digestive system, your pancreas performs two essential functions. It produces digestive juices and enzymes that help break down proteins, carbohydrates and fats so the food you eat can be digested in your small intestine. It also secretes the hormones insulin and glucagon that regulate the way your body metabolizes sugar (glucose).
In order to carry out these different functions, your pancreas needs both exocrine and endocrine tissue. Endocrine glands, such as your pituitary and adrenals, secrete hormones directly into your bloodstream. Exocrine glands release substances into ducts or tubes that empty into your small intestine.
Most of your pancreas is composed of exocrine cells that produce digestive enzymes and juices. These cells are arranged in clusters and connected to a series of small ducts. Pancreatic juices flow from the cells through the ducts into the main pancreatic duct, which leads to your duodenum. The last portion of the bile duct, which carries bile from your liver and gallbladder, joins with the pancreatic duct just before it empties into your small intestine.
Your pancreas also contains small "islands" of endocrine cells located within the exocrine tissue. These cells, called the islets of Langerhans, secrete insulin and glucagon, along with somatostatin, which helps control the function of the other endocrine hormones.
Types of pancreatic cancer
Most pancreatic tumors originate in the exocrine duct cells or in the cells that produce digestive enzymes (acinar cells). Called adenocarcinomas, these tumors account for nearly 95 percent of pancreatic cancers.
Tumors that begin in the islet cells (endocrine tumors) are much less common. When they do occur, they may cause the affected cells to produce too much hormone. For example, tumors in glucagon cells (glucagonomas) might cause excess amounts of glucagon to be secreted, while tumors in insulin cells (insulinomas) may lead to an overproduction of insulin.
Tumors can also develop in the ampulla of Vater — the place where your bile and pancreatic ducts empty into your small intestine. Called ampullary cancers, these tumors often block the bile duct, leading to jaundice. Because even a small tumor can obstruct the bile duct, symptoms of ampullary cancer usually appear earlier than do symptoms of other pancreatic cancers.
Why pancreatic cancer occurs
Healthy cells grow and divide in an orderly way. This process is controlled by DNA — the genetic material that contains the instructions for every chemical process in your body. When DNA is damaged, changes occur in these instructions. One result is that cells may begin to grow out of control and eventually form a tumor — a mass of malignant cells.
Yet less than 10 percent of pancreatic cancers result from an inherited tendency. A greater number are caused by environmental or lifestyle factors, including:
The vast majority of pancreatic cancers occur in people older than 60. Other important risk factors include:
When to seek medical advice
See your doctor if you experience an unexplained weight loss, abdominal pain or jaundice. Many problems other than cancer may cause similar symptoms, and your doctor will check for these conditions as well as for pancreatic cancer. If cancer is present, early diagnosis and treatment offer the best chance of recovery.