What are IPMNs (intraductal papillary mucinous neoplasms)?

Papillary neoplasms in pancreatic duct with mucin hypersecretion lead to duct dilation and chronic obstructive pancreatitis. Preneoplasmic lesions, histology shows hyperplasia to carcinoma regions w/in a single tumor. 3 groups, benign, bordeline, and malignant (invasive or non-invasive based on extension beyond basement membrane)