Background Non-invasive intraductal papillary mucinous neoplasm (IPMN) with high-grade dysplasia and IPMN-associated invasive pancreatic ductal adenocarcinoma (PDAC) are frequently included under the term “malignancy”. The goal of this study is to clarify the difference between these two entities. Methods From 1996 to 2013, data of 616 patients who underwent pancreatic resection for an IPMN were reviewed. Results The median overall survival for patients with IPMN with high-grade dysplasia (92 months) was similar to survival for patients with IPMN with low/intermediate-grade dysplasia (118 months, p = 0.081), and superior to that of patients with IPMN-associated PDAC (29 months, p < 0.001). IPMN-associated PDAC had lymph node metastasis in 53%, perineural invasion in 58%, and vascular invasion in 33%. In contrast, no lymph node metastasis, perineural or vascular invasion was observed with high-grade dysplasia. None of the patients with IPMN with high-grade dysplasia developed recurrence outside the remnant pancreas. In stark contrast 58% of patients with IPMN-associated PDAC recurred outside the remnant pancreas. The rate of progression within the remnant pancreas was significant in patients with IPMN with high-grade (24%) and with low/intermediate dysplasia (22%, p = 0.816). Conclusion Non-invasive IPMN with high-grade dysplasia should not be considered a malignant entity. Compared to patients with IPMN with low/intermediate-grade dysplasia, those with high-grade dysplasia have an increased risk of subsequent development of PDAC in the remnant pancreas.
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