What are the two types of cells pancreatic cancer starts in?

Pancreatic cancer starts in one of two kinds of cells. The National Cancer Institute says it "can develop from two kinds of cells in the pancreas: exocrine cells and neuroendocrine cells, such as islet cells."

The pancreas runs two separate businesses in one organ. Exocrine cells make digestive enzymes and pour them into ducts that drain into the small intestine. Neuroendocrine cells, gathered in small clusters called islets, make hormones and release them straight into the blood.

Which cell a tumor came from is the first fork in the road. Almost nothing after it is the same.

The exocrine side is nearly all of it

NCI's summary for clinicians reports that duct cell carcinoma makes up "90% of all cases." These tumors arise from the cells lining the drainage ducts rather than from the enzyme factories themselves.

This is the type most people mean by pancreatic cancer. NCI notes it "is more common and is usually found at an advanced stage." The 2025 figures for the United States, 67,440 new cases and 51,980 deaths, come from the American Cancer Society and are reprinted in NCI's summary.

NCI gives three reasons the diagnosis comes late. "There are no noticeable signs or symptoms in the early stages." When symptoms do arrive, they resemble other conditions, such as pancreatitis. And "the pancreas is obscured by other organs in the abdomen," which makes small tumors hard to see.

The neuroendocrine side is rare and behaves differently

NCI's summary on these tumors says they "originate in islet cells" and "account for less than 2% of pancreatic malignancies."

They also split again. NCI explains that "islet tumors may either be functional (produce one or more active hormones) or nonfunctional." Functional ones are named for the hormone they make, including insulinoma, gastrinoma, glucagonoma, VIPoma, and somatostatinoma.

The outlook is not the same either. NCI states these tumors "are less common but have a better prognosis" than the exocrine type. Anyone reading survival figures should check which of the two the numbers describe.

Two other labels on the report

Where in the pancreas the tumor sits matters too. NCI notes that cancers "are commonly identified by the site of involvement within the pancreas," meaning the head, body, tail, or uncinate process, and that "surgical approaches differ for masses" in each location.

You may also see CA 19-9, a substance measured in blood. NCI says "most patients with pancreatic cancer have an elevated CA 19-9 level at diagnosis," but also that "the presence of a normal CA 19-9 level does not preclude recurrence." It helps track a known cancer. It cannot rule one out.

The question that shapes everything

For exocrine pancreatic cancer, treatment planning turns on one classification. NCI describes four groups: resectable, meaning no involvement of nearby blood vessels; borderline resectable, where vessels are involved; locally advanced, where vessel invasion rules out surgery; and metastatic, meaning it has spread further.

That single word decides whether an operation is on the table, and whether chemotherapy comes first, last, or alone.

So two things belong in your notes after a pancreatic cancer diagnosis. Which cell type is it, exocrine or neuroendocrine? And if exocrine, which of those four groups applies right now? Ask for both in writing. The rest of the plan hangs on them.