Update on pancreatic intraepithelial neoplasia.

Pancreatic intraepithelial neoplasia (PanIN) is a histologically well-defined precursor to invasive ductal adenocarcinoma of the pancreas. PanINs are remarkably common lesions, particularly in the elderly population. Molecular studies have helped establish the progression of PanIN to invasive cancer, and recently genetically engineered mouse models have been generated that recapitulate the entire spectrum of lesions from precursor to invasive pancreatic cancer. Some PanIN lesions produce lobulocentric atrophy of the pancreatic parenchyma, and, when multifocal, this lobulocentric atrophy may be detectable using currently available imaging techniques such as endoscopic ultrasound. The association of acinar-ductal metaplasia with PanIN lesions has led some to hypothesize that PanINs develop from acinar cells that undergo acinar-ductal metaplasia.