| With the use of modern cross-sectional abdominal imaging modalities, an increasing number of IPMN of the pancreas are identified incidentally. IAP guideline 2012 of IPMN has contributed to improvement in management of IPMN, although several issues remain to be settled. Pathologically, IPMN has a wide spectrum from low-grade dysplasia, high-grade dysplasia (non-invasive) to invasive cancer. However, assessment of grade of dysplasia by histology has not be standardized. IPMNs are categorized into main duct and branch duct IPMNs. Most cases of main duct IPMN, particularly those with the main pancreatic duct of 10 mm or more, should undergo pancreatic resection, given the high risk of malignancy. On the other hand, branch duct IPMN has a relatively low incidence of malignancy, and the management is often controversial. The guideline stresses the importance of mural nodules and dilated main pancreatic duct as high-risk stigmata for predicting malignancy. However, sensitivity and specificity of preoperative diagnosis of malignancy are still suboptimal. The optimal criterion of mural nodule size is not determined. Furthermore, accurate distinction of malignant IPMN without mural nodules is difficult on imaging studies. Most cases of branch duct IPMN undergo non-operative follow-up. IPMN has a risk of concomitant pancreatic ductal adenocarcinoma as well as malignant transformation of IPMN. The optimal protocol of surveillance should be determined, including the interval and modalities of imaging studies, and the follow-up period. Concerning surgery, extended lymph node resection is unnecessary for IPMN. Particularly non-invasive IPMN rarely has node metastasis and limited resection without node dissection may be performed, although the accurate differentiation is often difficult by imaging studies. The number of cases of laparoscopic surgery, especially distal pancreatectomy, is increasing. In this lecture, I would like to pesent the current status in management of IPMN in Japan. |
