Update on the pathology and genetics of exocrine pancreatic tumors with ductal phenotype: precursor lesions and new tumor entities

The majority of pancreatic neoplasms show a ductal phenotype and can be classified as ductal adenocarcinomas. Pancreatic duct lesions have been discussed as tumor precursors. This review presents a recently adopted standard system for these lesions which distinguishes among three grades of pancreatic intraepithelial neoplasia (PanIN). Molecular studies revealed that PanIN-2 and PanIN-3 lesions represent a distinct step towards invasive carcinoma. Another focus of the review is the advances that have been made in the further immunohistochemical and molecular characterization of special pancreatic neoplasms showing a ductal phenotype, such as undifferentiated carcinoma, mucinous noncystic (colloid) carcinoma, intraductal papillary mucinous neoplasm, mucinous cystic neoplasm, medullary carcinoma, and other rare tumors.