The clinicopathologic features of intraductal papillary mucinous neoplasms of the pancreas.

Since first described in 1982, intraductal papillary mucinous neoplasm (IPMN) has been the preferred term to describe the proliferation of the pancreatic ductal epithelium. It is totally different from pancreatic carcinoma in epidemiology, histology, pathology and prognosis. According to the site of involvement, IPMNs are classified into three categories, i.e. main duct type, branch duct type, and combined type. Most branch duct IPMNs are benign, whereas the other two types are often malignant. A large branch duct IPMN and marked dilation of the main pancreatic duct indicate the presence of adenoma at least. The additional existence of large mural nodules increases the possibility of malignancy in all types. The prognosis is more favorable after complete resection of benign and non-invasive malignant IPMNs. Malignant IPMNs that become more aggressive after parenchymal invasion necessitate adequate lymph node dissection. On the other hand, asymptomatic branch duct IPMNs without mural nodules can be observed without the need for resection for a considerable period of time. Our review addresses available data, current understanding, controversy, and future directions about IPMNs.