What is cancer?

Cancer starts when cells in the body change (mutate) and grow out of control. Your body is made up of tiny building blocks called cells. Normal cells grow when your body needs them. They die when your body no longer needs them.

Cancer is made up of abnormal cells that grow even though your body doesn't need them. In most cancers, the abnormal cells grow to form a lump or mass called a tumor. If cancer cells are in the body long enough, they can grow into (invade) nearby tissues. They can even spread to other parts of the body (metastasize).

What is pancreatic cancer?

Pancreatic cancer is cancer that starts in your pancreas. Normal cells in the pancreas go through a series of changes that make them stop acting like normal cells. Over time, this can lead to excess cell growth, and tumors can form.

Understanding the pancreas

The pancreas is a large gland. It is a part of the digestive system. It's an organ that makes substances the body needs. It makes two important things:

• Enzymes for food digestion

• Hormones to help control the amount of sugar (glucose) in the blood

Your pancreas is in your left upper belly (abdomen) behind your stomach and below the liver. It’s about 6 inches long in adults. The end, toward the middle of your abdomen, is wide and is called the head. The middle is called the body. The narrow end on the left side of your abdomen is called the tail.

The pancreas is made up of two main types of cells:

The exocrine pancreas is made up of cells that make digestive juices. These help your body break down food. Most pancreatic cancers start in this part of the pancreas. Pancreatic juices contain chemicals called enzymes that help break down food into substances your body can use. The pancreas releases these enzymes during meals. The enzymes go into your small intestine through small tubes called ducts. The main pancreatic duct is at the head of the pancreas. It joins the common bile duct, which comes from the liver and gallbladder. The enzymes from the pancreas mix with other substances coming from the liver and gallbladder. The merged ducts open into the first part of the small intestine (called the duodenum). In the duodenum, the enzymes help break down fats, sugars, starches, and proteins in the food you eat.

The endocrine pancreas makes many hormones that are released into the blood. They help control how your body works. The pancreatic endocrine cells are arranged in small clumps called islets of Langerhans. Two important hormones made here are insulin and glucagon. These hormones help your body use and store the energy created from the food you eat. Insulin helps control the amount of sugar in your blood. A small number of all pancreatic cancers start in endocrine cells.

What are the types of cancer in the pancreas?

There are two main types of cancer that can start in the pancreas:

• Adenocarcinomas. These start in the exocrine pancreas cells that make up the pancreatic ducts or, less often, the cells that secrete digestive enzymes. They are also called pancreatic ductal adenocarcinoma (PDAC). About 95 out of 100 pancreatic cancers are adenocarcinomas. When people use the term pancreatic cancer, they usually mean this type.

• Pancreatic neuroendocrine tumors (PNETs). These tumors are also called islet cell tumors. They start in endocrine cells in the pancreas. There are many types of PNETs. They're named based on the type of hormone they make. They can be non-cancer (benign) or cancer (malignant). They can be nonfunctioning (don't make hormones) or functioning (make hormones). Fewer than 10 out of 100 pancreatic cancers are PNETs.

Other types of cancer that can start in the pancreas are much less common. They include rare exocrine cancers like acinar cell carcinomas, adenosquamous carcinomas, squamous cell carcinomas, signet ring cell carcinomas, and giant cell tumors.

How pancreatic cancer grows and spreads

Pancreatic cancer often grows within the pancreas for a long time before it causes any symptoms. If the cancer grows outside the pancreas, it often goes into the nearby bile ducts and lymph nodes in your belly (abdomen). Sometimes it spreads to other nearby tissues. Pancreatic cancer may also spread to distant parts of the body. These can include your liver or lungs.

When pancreatic cancer spreads to another part of the body, it’s not a new cancer. For instance, if it spreads to the liver, it’s not called liver cancer. It’s called metastatic pancreatic cancer. The cancer cells in the liver look like, act like, and are treated like pancreatic cancer.

Talk with your healthcare provider

If you have questions about pancreatic cancer, talk with your healthcare provider. Your healthcare provider can help you understand more about this cancer.