The pancreas sits just behind the stomach and is closely connected to the bile duct, which connects the liver to the small bowel. It produces digestive juices that break down food, as well as hormones like insulin that control blood sugar. Pancreatic cancer develops when some of the cells in the pancreas start to grow in an uncontrolled way. Most cases are down to factors such as aging, smoking, diabetes and obesity, but genetic changes and family history can also play a role. Chronic pancreatitis, where long-term inflammation makes it easier for abnormal cancer cells to develop, can also contribute to risk.
One of the things that makes pancreatic cancer difficult to treat is the way the tumour interacts with the tissue around it. Instead of forming a soft lump, it often triggers the body to lay down dense scar-like tissue around the tumour. We call this a desmoplastic reaction, and it can act as a barrier by reducing blood supply and making it harder for chemotherapy drugs to penetrate and work effectively.
The cancer cells themselves have a tendency to invade nearby nerves and blood vessels, which is why surgery is often challenging. They also tend to spread quite quickly to the liver or the lining of the abdomen (peritoneum). Understanding these features has led to new treatments — such as more intensive chemotherapy combinations and highly targeted radiotherapy — designed to overcome these barriers.
Types of pancreatic cancer
Pancreatic ductal adenocarcinoma (the most common)
What it is
Arises from the exocrine cells of the pancreas, which normally make digestive juices.
How it usually behaves
Accounts for around 90% of cases. Tends to grow quickly and spread early to nearby lymph nodes, vessels, and liver. This is the type most people mean when they say ‘pancreatic cancer.’
Neuroendocrine tumours (NETs)
What it is
Develop from the hormone-producing (endocrine) cells of the pancreas.
How it usually behaves
Can behave very differently — some are slow-growing and may cause symptoms from hormone overproduction, while others are more aggressive.
Cystic tumours (e.g. IPMN, mucinous cystic neoplasm)
What it is
Growths that form fluid-filled sacs in the pancreas.
How it usually behaves
Some are benign, others can turn malignant over time. Often found on scans before causing symptoms and may be removed to prevent progression.
Rare exocrine tumours (e.g. acinar cell carcinoma, pancreatoblastoma)
What it is
Arise from other exocrine cells that make digestive enzymes.
How it usually behaves
Much less common; can behave aggressively but treatment approaches are tailored individually.
How does pancreatic cancer cause illness?
Although it begins in the pancreas, pancreatic cancer is best understood as a systemic illness. This means it often affects the whole body, not just the pancreas itself. Even when the tumour is still localised and has not spread, it can release chemical signals that disrupt normal body functions. This can lead to cancer cachexia, a syndrome of weight loss, muscle wasting, and fatigue that is out of proportion to food intake. Cachexia often can’t be reversed with diet alone, but recognising it early is important. Specialist support with nutrition, enzyme replacement, exercise, and medication can help you maintain strength, improve energy, and cope better with treatment.
Other systemic effects include changes in blood sugar, blood clotting, and immune function. These features are part of why pancreatic cancer feels so exhausting, and why treatment needs to address not just the cancer but also your overall wellbeing. By recognising and managing these systemic effects early, we can often help patients feel stronger and better able to tolerate treatment.