[Neoplastic intraepithelial lesions of pancreatic ducts: new entities]

Intraductal neoplastic lesions of the pancreas have been the focus of recent efforts aiming to better characterize several entities. Beside reactive papillary hyperplastic lesion of pancreatic ducts whose limits and significance are unclear, two different entities, intraductal papillary mucinous neoplasm (IPMN) with its variant intraductal oncocytic papillary neoplasm, and pancreatic intraepithelial neoplasia (PanIN), the precursors of pancreatic adenocarcinoma have been recognized. Each has been carefully described at the microscopic level with classification into several grades of dysplasia. IPMNs are intraductal, papillary, often diffuse and mucus hypersecreting neoplastic lesions. Mucin accumulation gives to the lesion a cystic pattern. Treatment is surgical resection of the whole lesion. Intraductal oncocytic papillary neoplasm is a rare variant of IPMN. The prognosis of IPMN is globally favorable, but these tumors display the risk of malignant transformation into a mucinous or a tubular pancreatic adenocarcinoma. Although IPMN can induce symptoms, PanIN are silent and always discovered at the vicinity of an invasive adenocarcinoma. The usefulness and the reproducibility of the classification of PanIN remain to be determined. PanIN classification might resume the different successive steps of molecular genetic or epigenetic events associated with the development of a pancreatic carcinoma.