Pancreatic cancer most often originates in the cells lining the ducts of the pancreas, a gland located behind the stomach that produces hormones (including insulin) and digestive juices. The cancer develops when cells in the pancreas acquire changes (mutations) in their DNA that cause them to grow uncontrollably and form a tumor, typically starting as pancreatic ductal adenocarcinoma, the most common type. Less commonly, the cancer can begin in the hormone-producing or neuroendocrine cells of the pancreas. The exact cause of pancreatic cancer is not fully understood, but it is linked to DNA mutations that may be inherited or occur over time due to environmental or lifestyle factors. Risk factors include smoking (a major cause), obesity, chronic pancreatitis, diabetes, older age, certain inherited genetic mutations or syndromes, family history, and exposure to certain chemicals. About 10% of pancreatic cancers are thought to be familial or hereditary. In summary, pancreatic cancer arises from abnormal changes in the DNA of pancreatic cells, especially the duct cells, which lead to unchecked cell growth and tumor formation. Multiple risk factors contribute to the likelihood of these changes occurring.