What is Pancreatic Cancer?
Pancreatic cancer is a type of cancer that begins in the cells of the pancreas, a small organ located behind the stomach that helps in the digestion of food and the regulation of blood sugar. Pancreatic cancer — a type of gastrointestinal cancer, or cancer that begins in the digestive organs — is caused by changes, or mutations, in the DNA of pancreatic cells, which cause them to multiply abnormally into cancer cells.
About 1 out of 10 people with pancreatic cancer have an inherited genetic mutation that may have increased their risk of developing the condition. Most cases of pancreatic cancer occur after birth. People who develop this type of cancer typically do not have many symptoms until pancreatic cancer progresses or has become advanced. Most people diagnosed with pancreatic cancer are older than 45 years old.
Types of Pancreatic Cancer
Pancreatic cancer is classified into two major categories — exocrine pancreatic cancer and neuroendocrine pancreatic cancer — within which several different types exist.
Exocrine (nonendocrine) pancreatic cancer
Exocrine pancreatic cancer originates in the exocrine cells, which comprise the exocrine gland of the pancreas. This gland creates enzymes that help break down food for digestion. Exocrine cells also make up the ducts of the pancreas. The pancreatic ducts transport secreted digestive enzymes into the first part of the small intestine (duodenum). More than 95% of all pancreatic tumors are exocrine tumors.
The most common types of exocrine pancreatic cancers include:
Adenocarcinoma, sometimes referred to as ductal carcinoma, is the most prevalent type of exocrine pancreatic cancer. Adenocarcinoma begins in the pancreatic duct linings, and accounts for 90% of pancreatic cancers diagnosed.
Acinar cell carcinoma is another type of adenocarcinoma, accounting for just 1–2% of exocrine pancreatic cancers. Acinar cell carcinoma originates from the cells that create pancreatic enzymes, which produce pancreatic juice to help the duodenum (a part of the small intestine) break down food.
Squamous cell carcinoma
Another type of exocrine pancreatic cancer, squamous cell carcinoma develops in the pancreatic ducts and is caused by squamous cells, which are not typically present in the pancreas. Squamous cells are found in the lining of digestive tracts (as well as in the lining of respiratory tracts and the middle and top layers of the skin). This is an extremely rare type of pancreatic cancer, and more studies must be done to fully understand its origins.
Adenosquamous carcinoma is a rare, aggressive type of cancer, making up just 1–4% of exocrine pancreatic cancers. In these cases, the tumors have ductal adenocarcinoma and squamous cell carcinoma characteristics.
Making up 1–3% of exocrine pancreatic cancers, colloid carcinoma, also known as mucinous non-cystic carcinoma, typically develops from a type of benign cyst called an intraductal papillary mucinous neoplasm (IPMN). In this type of cancer, the tumor is made up of malignant cells that float in mucin — a type of protein found in saliva, gastric juices, and other bodily fluids. This means the cancer is not likely to spread and allows for better treatment and prognosis.
Neuroendocrine pancreatic cancer
Neuroendocrine pancreatic cancer originates in the neuroendocrine cells of the pancreas. These neuroendocrine cells (sometimes just called endocrine cells) are grouped in small clusters called islets. Islets produce important hormones, including insulin and glucagon, which regulate the glucose (sugar) level in the blood, as well as somatostatin, which inhibits insulin and glucagon secretion. Neuroendocrine tumors (NETs), also referred to as endocrine or islet cell tumors, account for less than 5% of pancreatic cancers.
There are a few main types of neuroendocrine pancreatic tumors:
Gastrinoma tumors develop in the neuroendocrine cells that make a hormone called gastrin, which helps in the digestion of food. When a tumor forms in the gastrin-producing cells, it is called gastrinoma. These tumors are rare.
Insulinoma tumors develop in the neuroendocrine cells within the pancreas that produce insulin cells. Insulin helps control the amount of glucose, or sugar, in the bloodstream. When a tumor develops within these cells, it is referred to as insulinoma. These rare tumors create more insulin than the body can use, resulting in low blood sugar.
Glucagonoma tumors develop in the pancreatic neuroendocrine cells that create glucagon, a hormone that helps regulate the amount of glucose (sugar) in the bloodstream. When these rarer tumors form, the amount of glucose in the body increases, which can lead to serious health problems — collectively called glucagonoma syndrome.
There are also other types of neuroendocrine tumors, including VIPomas, which affect vasoactive intestinal peptides, or VIPs (hormones that aid in digestion), and somatostatinomas, which affect somatostatin (a hormone that helps regulate various bodily functions). These types of tumors are often categorized together because they are treated in similar ways.
Stages of Pancreatic Cancer
There are various stages of pancreatic cancer, determined by the size of the tumor and the level of metastasis — how much the cancer has spread to organs, tissues, or lymph nodes. Staging helps doctors create a personalized treatment plan for each patient.
- Stage 0 —At stage 0, the cancer is in the top layers of the pancreatic duct and has not spread elsewhere. This stage is sometimes referred to as carcinoma in situ.
- Stage 1 — At stage 1, the cancer is still found only within the cells of the pancreatic duct and has not spread to lymph nodes or other organs. Stage 1 also is broken down into two sub-stages:
- Stage 1A — The tumor is 2 centimeters or smaller.
- Stage 1B — The tumor is bigger than 2 centimeters.
- Stage 2 — At stage 2, the cancer may have spread to nearby lymph nodes, tissue, or organs. Stage 2 is also broken up into two sub-stages:
- Stage 2A — At stage 2A, the cancer has spread to nearby organs or tissues. It has not spread to nearby lymph nodes, major blood vessels, or nerves, nor has it spread to distant areas of the body.
- Stage 2B — The cancer has spread to nearby lymph nodes at stage 2B. It may have spread to nearby organs and tissues as well, but it has not spread to major blood vessels or nerves. As with stage 2A, it has not spread to distant areas of the body.
- Stage 3 — Stage 3 pancreatic cancer indicates that cancer may have spread to large blood vessels near the pancreas, or to nearby lymph nodes. It has not spread to more distant areas of the body.
- Stage 4 — At stage 4, the cancer may be any size. It may have spread to distant organs, such as the liver, lungs, bones, or peritoneal cavity (the lining of the abdominal cavity). It may also have spread to the lymph nodes or nearby organs and tissues near the pancreas.
Symptoms & Signs of Pancreatic Cancer
Because the pancreas is so deep within the body, it can be difficult to spot tumors early. People with pancreatic cancer often have no symptoms or signs. However, several common indicators indicate that the cancer has spread outside of the pancreas or grown in size.
The most common signs and symptoms of pancreatic cancer include:
- Weight loss or poor appetite
- Jaundice (yellowing of the eyes and skin, including the gums and inner lips)
- Digestive problems
- Clay-colored, greasy, floating, or particularly foul-smelling stools
- Dark urine
- Stomach, upper back, or arm pain
- Nausea or vomiting
- Itchy skin
- Blood clots (may cause arm or leg swelling)
- Gallstones (causing rapidly worsening pain in the abdomen)
- Itchy skin, palms, and soles of feet
Causes of Pancreatic Cancer
The exact cause of pancreatic cancer is still unknown in most cases. The gene mutations that cause it can be either inherited or acquired:
- Inherited gene mutations. Approximately 10% of all pancreatic cancer cases are inherited through mutations in the DNA. These mutations are called germline mutations, and they can be passed down from generation to generation.
- Acquired gene mutations. Most cases of pancreatic cancer are caused by acquired gene mutations. In other words, the genes become mutated throughout a person’s lifetime. These mutations cannot be passed down from a parent to a child.
Certain factors can also increase the risk of pancreatic cancer, whether one has acquired or inherited gene mutations.
Risk Factors for Pancreatic Cancer
Although the exact cause of pancreatic cancer cases is usually unknown, several factors can increase the risk:
- Diabetes. People with diabetes may be at higher risk of pancreatic cancer, especially when someone has had it for many years. People who suddenly develop diabetes as an adult should consult with a doctor, as this can be an initial sign of pancreatic cancer.
- Age. The risk of developing pancreatic cancer increases with age. Most people who develop this kind of cancer are older than 45.
- Sex. Men are diagnosed with pancreatic cancer slightly more often than women.
- Race/ethnicity. Black people and people of Ashkenazi Jewish heritage or more likely to develop pancreatic cancer than Hispanic, white, or Asian people.
- Lifestyle. A high-fat diet, chronic alcohol use, tobacco use, and a sedentary lifestyle can all increase the risk of developing pancreatic cancer.
- Infections. Some infections, especially those of the stomach or gums, may elevate pancreatic cancer risk. In particular, bacteria called Helicobacter pylori, or H. pylori, can cause inflammation, pain, and ulcers in the stomach. This bacteria primarily increases the risk of stomach cancer, but it can increase the risk of pancreatic cancer as well.
- Some autoimmune conditions. Certain autoimmune conditions, such as Sjögren’s disease or lupus, can make one more susceptible to cancer of the pancreas.
- Some inherited conditions. Certain inherited conditions, including Li-Fraumeni syndrome (LFS) and Familial adenomatous polyposis (FAP) can make one more likely to develop pancreatic cancer.
- Injury or trauma to the pancreas. Pancreas injury or trauma can lead to pancreatitis (chronic inflammation of the pancreas), which in turn can increase one’s risk of pancreatic cancer.
How to Prevent Pancreatic Cancer
While there is no surefire way to avoid pancreatic cancer, as the DNA mutations that cause it can be either inherited or acquired, people can reduce their risk by:
- Quitting tobacco. Smoking makes people two to three times as likely to develop pancreatic cancer. Quitting smoking or ceasing the use of other tobacco products can significantly reduce one’s risk of pancreatic cancer, as well as many other types of cancer.
- Improving diet. People who eat a lot of high-fat foods are more at risk for pancreatic cancer. One can reduce one’s risk by maintaining a healthy diet that is low in sugary and fatty foods.
- Reducing alcohol intake. Heavy drinking can increase risk by causing consistent inflammation of the pancreas, known as pancreatitis.
- Maintaining a healthy weight and lifestyle. People who are obese or even overweight have an increased risk of pancreatic cancer. Exercising regularly, along with getting enough sleep and improving one’s diet, can decrease the risk of cancer.
- Reducing chemical exposure. Exposure to pesticides, certain dyes, petrochemicals (chemicals made from crude oil and natural gas) and benzene (found in crude oil) can elevate the risk of pancreatic cancer. People who work with chemicals should take the proper precautions to minimize risk.
- Genetic testing. If you have a family history of pancreatic cancer, genetic testing may be right for you and/or your family members. If you have any family with pancreatic cancer, they can undergo testing to determine if they carry inherited mutations that they could have passed down to you. If you know that a parent has a mutation or if they cannot be tested, you may want to get tested yourself to help determine your risk of developing cancer and whether you could pass on mutations to your children. You should consult with a doctor to determine the best course of action.