Intraductal papillary mucinous neoplasms of the pancreas.

The introduction of the exocrine pancreatic classification by the World Health Organization and improvements in pancreatic imaging have led to an improved understanding of intraductal papillary mucinous neoplasms (IPMNs) of the pancreas. As a result, IPMNs of the pancreas are increasingly being recognized as a separate disease entity. IPMNs are characterized by the cystic dilatation of the pancreatic duct and its branches, with papillary projections. There are three histological subtypes of IPMNs: main duct, branch duct, and mixed. The degree of atypia ranges from adenoma to frank invasive carcinoma. The lymph nodes are involved considerably less frequently than they are in pancreatic adenocarcinoma. Most patients are symptomatic at diagnosis and require a diagnostic workup similar to that for patients with pancreatic adenocarcinoma. Although some investigators continue to advocate total pancreatectomy, the evidence in support of this is decreasing. Partial pancreatectomy remains the treatment option. Intraoperative assessment of the resection surgical margins is an important component of surgical resection. Additionally, controversy also exists regarding the nature of the follow-up and the need for adjuvant chemoradiation therapy in the patient. Unlike ductal adenocarcinomas, IPMNs follow a relatively indolent course; the 5-year survival rate in patients with invasive IPMNs is 57%. A mural nodule and a main pancreatic duct diameter greater than 5 mm have been found to be predictors of malignancy.