Histologically distinct noninvasive precursor lesions have been recognized in the pancreas for close to a century. The recent development of a consistent reproducible nomenclature and classification system for these lesions has been a major advance in the study of these noninvasive precursors. The “pancreatic intraepithelial neoplasia” or PanIN system was developed at a National Cancer Institutes sponsored think tank in Park City, Utah. Numerous studies have now demonstrated that genetic alterations in cancer-associated genes are more common in higher grade PanIN lesions then they are in lower grade PanIN lesions, and that higher grade PanIN lesions have many of the same genetic alterations that are found in invasive ductal adenocarcinomas of the pancreas. Thus, just as there is a progression in the colorectal of adenomas to invasive adenocarcinoma, so too is there a progression in the pancreas of histologically low-grade PanIN, to high-grade PanIN to invasive ductal adenocarcinoma.