Pancreatic intraepithelial neoplasia.

Great efforts have been devoted to detecting preinvasive precursors to ductal carcinoma of the pancreas in the hope of improving the currently bleak prognosis of invasive pancreatic cancer. Intensive investigations of the pancreas have led to the recognition of intraductal papillary mucinous neoplasms (IPMNs) and the detection of preinvasive precursors to conventional ductal carcinoma. The pancreatic intraepithelial neoplasia (PanIN) nomenclature for precursor lesions of ductal carcinoma was developed at the "Pancreatic Cancer Think Tank" held in the United States in 1999. However, some reports of precursor lesions have suggested that these definitions do not encompass the full spectrum of precursors of ductal carcinoma, and these issues were the subject of the "Forum on Carcinoma In Situ of the Pancreas" held in Japan in 2002. After this forum, it became clear that the existing definitions of PanINs needed to be revised and expanded. Both participants of the Pancreatic Cancer Think Tank and the Forum gathered together at a meeting on precursor lesions of pancreatic cancer in 2003, and an international consensus on the diagnostic criteria for PanINs and IPMNs was created. We describe herein the current understanding of precursor lesions of pancreatic cancer.