Understanding Pancreatic Cancer

What Is Pancreatic Cancer?

Last updated and reviewed on June 24, 2026.

Pancreatic cancer is a disease in which cells inside the pancreas begin to grow in ways they should not. Every cell in your body has instructions written in its DNA that tell it when to grow, when to divide, and when to stop. When something disrupts those instructions, a cell can start multiplying without any brakes, eventually forming a clump of abnormal cells called a tumor. When that happens in the pancreas, it is called pancreatic cancer.

Pancreatic cancer is one of the more serious cancers because it tends to be found late, after the tumor has already grown large or spread to other parts of the body. This happens partly because the pancreas sits deep inside the abdomen, hidden behind other organs, and partly because early pancreatic cancer often does not cause noticeable symptoms. Understanding what pancreatic cancer is, where it starts, and how it affects the body is an important part of navigating a diagnosis.

What Is the Pancreas?

The pancreas is a flat, fish-shaped gland about 6 inches long that sits in the back of the abdomen, tucked behind the stomach. It has two main parts that do very different jobs, and this is important because most pancreatic cancers start in one specific part.

The first part is called the exocrine pancreas. About 95 percent of the pancreas is made up of exocrine tissue. These cells produce digestive juices (called pancreatic enzymes) that flow through a tube called the pancreatic duct into the small intestine, where they help break down food, especially fats and proteins. When pancreatic cancer doctors talk about "pancreatic cancer," they almost always mean cancer that started in the exocrine pancreas.

The second part is called the endocrine pancreas. This part is made up of small clusters of hormone-producing cells scattered throughout the gland, called the islets of Langerhans. These cells produce hormones that go directly into the bloodstream, including insulin and glucagon, which control blood sugar levels. Tumors that start here are called pancreatic neuroendocrine tumors (PNETs), and they behave very differently from exocrine pancreatic cancer.

The pancreas is divided into three sections:

• The head (the wide right side, which sits next to the first part of the small intestine, called the duodenum)
• The body (the middle section)
• The tail (the narrow left side, which sits near the spleen)

About 70 percent of pancreatic cancers start in the head of the pancreas.

How Does Pancreatic Cancer Start?

Pancreatic cancer starts when DNA changes, called mutations, build up inside a pancreatic cell over time. These mutations can occur by chance, or they can be influenced by factors like smoking, chronic inflammation of the pancreas (called pancreatitis), or inherited gene changes that a person was born with. Once enough mutations have accumulated, the cell ignores the normal signals that keep cell growth in check, and it starts dividing without stopping.

• PanIN: In the exocrine pancreas, cancers usually develop through a series of precancerous changes that happen slowly over many years before a tumor forms. One of the most studied of these precancerous changes is called pancreatic intraepithelial neoplasia (PanIN).

PanIN lesions are microscopic changes in the cells lining the pancreatic ducts, and they can gradually progress from low-grade abnormalities to full-blown cancer over a period of 10 to 15 years. This long precancer period is one reason researchers believe that earlier detection could save lives if reliable screening tools can be developed.

Precancerous Conditions

• IPMNs: Iintraductal papillary mucinous neoplasms (IPMNs), which are cyst-forming tumors inside the pancreatic duct that can become cancerous over time
• Mucinous cystic neoplasms (MCNs), which are cysts mostly found in the body and tail of the pancreas.

These conditions are followed closely with imaging when discovered, because some have a higher risk of turning into cancer.

Where Does Pancreatic Cancer Start?

Most pancreatic cancers start in the cells that line the pancreatic ducts, which are the tubes that carry digestive juices through the pancreas and into the small intestine. Because the pancreatic duct runs through the head of the pancreas before joining the bile duct to enter the duodenum, most pancreatic cancers arise in the head of the pancreas.

Cancers in the head of the pancreas often press on the bile duct early in their growth, blocking the flow of bile and causing the skin and eyes to turn yellow (a symptom called jaundice). This means cancers in the head may actually be noticed slightly sooner than those in the body or tail, where there are fewer structures to compress, and symptoms tend to develop later.

Pancreatic neuroendocrine tumors (PNETs) can arise anywhere in the pancreas. Some of them produce hormones in large amounts, causing recognizable hormonal syndromes. Others are non-functioning and do not produce detectable hormone effects. PNETs generally have a better prognosis than exocrine pancreatic cancer.

How Does Pancreatic Cancer Affect the Body?

Pancreatic cancer affects the body in several interconnected ways. The physical effects depend on where in the pancreas the tumor is located, how large it has grown, and whether it has spread beyond the pancreas.

As the tumor grows, it can press on or grow into nearby structures. A tumor in the head of the pancreas often compresses the bile duct, causing bile to back up into the blood and tissues and leading to jaundice, dark urine, pale stools, and itching. A growing tumor can also press on the stomach, small intestine, or major blood vessels, interfering with digestion and blood flow. Pain, when it occurs, is often caused by the tumor pressing on nerves in the back of the abdomen, which is why pancreatic cancer pain is often felt in the upper abdomen and radiates to the back.

Beyond the local effects, pancreatic cancer can disrupt the pancreas's function. If cancer destroys enough exocrine tissue, the body cannot produce enough digestive enzymes, leading to malabsorption of nutrients, weight loss, fatty stools (called steatorrhea), and diarrhea. If the endocrine tissue is affected, new-onset diabetes or worsening of existing diabetes can occur. Many patients with pancreatic cancer develop diabetes or notice that blood sugar control becomes harder, sometimes even before the cancer is formally diagnosed.

When pancreatic cancer spreads, it most commonly travels to the liver, the lining of the abdominal cavity (called the peritoneum), the lungs, and nearby lymph nodes. Spread to the liver is particularly common and can cause liver enlargement, pain in the upper right abdomen, and further disruption of digestion and metabolism.

What Are the Types of Pancreatic Cancer?

The word "pancreatic cancer" covers several distinct tumor types. Knowing which type you have matters enormously, because the types differ in how they grow, how they are treated, and what outcomes to expect.

• Pancreatic Ductal Adenocarcinoma (PDAC): This is by far the most common type of pancreatic cancer, making up about 90 to 95 percent of all cases. It starts in the cells that line the pancreatic ducts and is the type of cancer people usually mean when they say "pancreatic cancer." PDAC is known for being aggressive and for resisting many treatments. It is typically the type associated with the statistics you may have read about pancreatic cancer survival.
• Pancreatic Neuroendocrine Tumors (PNETs): These tumors start in the hormone-producing cells of the pancreas. They are less common than PDAC and generally behave more slowly, though some can be aggressive. PNETs are further classified as functioning (they produce excess hormones and cause recognizable symptoms like very low blood sugar or severe ulcers) or non-functioning (they do not produce enough hormone to cause obvious effects). Examples of functioning PNETs include insulinoma (produces excess insulin), gastrinoma (produces excess gastrin), and glucagonoma (produces excess glucagon). PNETs are sometimes called islet cell tumors.
• Acinar Cell Carcinoma: A rare type that starts in the acinar cells, which produce digestive enzymes. It makes up about 1 to 2 percent of all pancreatic cancers and can sometimes be associated with unusual fat breakdown in the body.
• Ampullary Cancer (Cancer of the Ampulla of Vater): Not technically a pancreatic cancer, but often grouped with it because of its location. The ampulla of Vater is the tiny opening where the pancreatic duct and bile duct empty into the small intestine. Cancers here tend to cause jaundice early and are often caught at an earlier stage, which gives them a better prognosis than typical PDAC.
• Cystic Tumors of the Pancreas: Some pancreatic tumors form cysts (fluid-filled sacs). Most pancreatic cysts are benign, but some have cancer potential. The main types with malignant potential include intraductal papillary mucinous neoplasms (IPMNs) and mucinous cystic neoplasms (MCNs). These are monitored closely or surgically removed depending on their characteristics.

What Are the Related Conditions to Pancreatic Cancer?

A few conditions are related to pancreatic cancer either because they raise the risk of developing it or because they can sometimes be confused with it during diagnosis.

• Chronic pancreatitis is a long-term inflammation of the pancreas that raises the risk of pancreatic cancer, particularly in people who have had it for many years. Chronic pancreatitis can cause many of the same symptoms as pancreatic cancer, including abdominal pain, weight loss, and digestive problems, which sometimes makes it hard to tell the two apart without imaging and biopsy.
• Pancreatic cysts are fluid-filled sacs that form in the pancreas. Most are benign, but certain types (especially IPMNs and MCNs) have a risk of turning into cancer. Many cysts are found incidentally on imaging done for other reasons, and whether to watch them or remove them is a common clinical question.
• New-onset diabetes in adults over 50 can sometimes be an early sign of pancreatic cancer, particularly when diabetes appears suddenly in someone who is not overweight and has no family history of diabetes. This relationship between diabetes and pancreatic cancer is an active area of research for early detection.
• Autoimmune pancreatitis (AIP) is a rare inflammatory condition of the pancreas caused by the immune system attacking pancreatic tissue. It can form a mass in the pancreas that looks like cancer on imaging, and it can cause jaundice and abdominal pain. It is important to distinguish AIP from cancer before any surgical decisions are made, because AIP often responds dramatically to steroid treatment.

What Are the Genetic and Risk Factors?

Most pancreatic cancers develop in people without a known inherited cause. However, about 10 percent of pancreatic cancers are linked to inherited gene mutations that can be passed down through families. Knowing whether you carry one of these mutations has real implications for your family members, for your own surveillance, and sometimes for treatment choices.

The most important hereditary syndromes associated with pancreatic cancer include:

• BRCA1 and BRCA2 gene mutations are most widely known for raising the risk of breast and ovarian cancer, but they also significantly raise the risk of pancreatic cancer. People with BRCA2 mutations have a roughly 3 to 10 times higher lifetime risk of pancreatic cancer compared to the general population.
• Lynch syndrome (hereditary nonpolyposis colorectal cancer, or HNPCC) is caused by mutations in the MLH1, MSH2, MSH6, or PMS2 genes and raises the risk of colorectal cancer, endometrial cancer, and several other cancers, including pancreatic cancer.
• Familial atypical multiple mole melanoma (FAMMM) syndrome is caused by mutations in the CDKN2A gene and raises the risk of both melanoma and pancreatic cancer.
• Hereditary pancreatitis is caused by mutations in the PRSS1 or SPINK1 genes and causes recurrent episodes of pancreatitis starting in childhood or early adulthood. People with hereditary pancreatitis have a significantly elevated lifetime risk of developing pancreatic cancer.
• Peutz-Jeghers syndrome is caused by mutations in the STK11 gene. It causes polyps in the digestive tract and raises the risk of several cancers, including pancreatic cancer.
• Familial pancreatic cancer refers to families in which two or more first-degree relatives have had pancreatic cancer without a clear inherited syndrome. The genetic basis of many of these families is still being studied.
• Non-hereditary risk factors include smoking, obesity, type 2 diabetes, chronic pancreatitis, heavy alcohol use, age, and certain occupational chemical exposures. These are covered in more detail in the Risk Factors guide.

What Are the Related Cancers to Pancreatic Cancer?

Pancreatic cancer has meaningful connections to several other cancers. Because BRCA1 and BRCA2 mutations raise the risk of breast cancer, ovarian cancer, and pancreatic cancer, a family history of breast or ovarian cancer may be relevant to a person's pancreatic cancer risk. Similarly, Lynch syndrome connects pancreatic cancer to colorectal, endometrial, ovarian, and several other cancer types.

Cancers near the pancreas can sometimes be difficult to distinguish from pancreatic cancer. Bile duct cancer (cholangiocarcinoma), gallbladder cancer, and duodenal cancer all arise in structures close to the pancreas and can share similar symptoms and imaging findings. Accurate diagnosis is essential before any treatment decisions are made, because the treatments for these different cancers can differ significantly.

Sources:

1. American Cancer Society. What Is Pancreatic Cancer? https://www.cancer.org/cancer/types/pancreatic-cancer/about/what-is-pancreatic-cancer.html
2. National Cancer Institute. Pancreatic Cancer Treatment (PDQ) Patient Version. https://www.cancer.gov/types/pancreatic/patient/pancreatic-treatment-pdq
3. Rahib L, et al. Projecting Cancer Incidence and Deaths to 2030. Cancer Research. 2014;74(11):2913-2921. https://pubmed.ncbi.nlm.nih.gov/24840647/
4. Siegel RL, Miller KD, Jemal A. Cancer Statistics, 2024. CA: A Cancer Journal for Clinicians. 2024;74(1):12-49. https://acsjournals.onlinelibrary.wiley.com/doi/full/10.3322/caac.21820
5. Pancreatic Cancer Action Network. About Pancreatic Cancer. https://www.pancan.org/facing-pancreatic-cancer/about-pancreatic-cancer/
6. Ryan DP, Hong TS, Bardeesy N. Pancreatic Adenocarcinoma. New England Journal of Medicine. 2014;371(11):1039-1049. https://pubmed.ncbi.nlm.nih.gov/25207767/
7. National Comprehensive Cancer Network (NCCN). NCCN Clinical Practice Guidelines: Pancreatic Adenocarcinoma. 2024. https://www.nccn.org/guidelines/guidelines-detail?category=1&id=1455