The exocrine cells and endocrine cells of the pancreas form different types of tumors. It’s very important to distinguish between exocrine and endocrine cancers of the pancreas. They have distinct risk factors and causes, have different signs and symptoms, are diagnosed using different tests, are treated in different ways, and have different outlooks.
Exocrine tumors: Exocrine tumors are by far the most common type of pancreas cancer. When someone says that they have pancreatic cancer, they usually mean an exocrine pancreatic cancer.
Pancreatic adenocarcinoma: An adenocarcinoma is a cancer that starts in gland cells. About 95% of cancers of the exocrine pancreas are adenocarcinomas. These cancers usually begin in the ducts of the pancreas. But sometimes they develop from the cells that make the pancreatic enzymes, in which case they are called acinar cell carcinomas.
Less common types of cancers: Other cancers of the exocrine pancreas include adenosquamous carcinomas, squamous cell carcinomas, signet ring cell carcinomas, undifferentiated carcinomas, and undifferentiated carcinomas with giant cells. These types are distinguished from one another based on how they look under the microscope.
Solid pseudopapillary neoplasms (SPNs): These are rare, slow-growing tumors that almost always occur in young women. Even though these tumors tend to grow slowly, they can sometimes spread to other parts of the body, so they are best treated with surgery. The outlook for people with these tumors is usually very good.
Ampullary cancer (carcinoma of the ampulla of Vater): This cancer starts in the ampulla of Vater, which is where the bile duct and pancreatic duct come together and empty into the small intestine. Ampullary cancers aren’t technically pancreatic cancers, but they are included in this document because their treatments are very similar.
Endocrine tumors: Tumors of the endocrine pancreas are uncommon, making up less than 4% of all pancreatic cancers. As a group, they are sometimes known as pancreatic neuroendocrine tumors (NETs) or islet cell tumors. Pancreatic NETs can be benign or malignant (cancer). Benign and malignant tumors can look alike under a microscope, so it isn’t always clear whether or not a pancreatic NET is cancer. Sometimes the diagnosis only becomes clear when the tumor spreads outside of the pancreas.
Non-functioning tumors: These tumors don’t make enough excess hormones to cause symptoms. They are more likely to be cancer than functioning tumors. Because they don’t make excess hormones that cause symptoms, they can often grow quite large before they are found.
Carcinoid tumors: These are another type of NET that rarely can start in the pancreas, although they are much more common in other parts of the digestive system. These tumors often make serotonin (also called 5-HT) or its precursor, 5-HTP.
The treatment and outlook for pancreatic NETs depend on the specific tumor type and the stage (extent) of the tumor, but the outlook is generally better than that of pancreatic exocrine cancers.