Perineural Invasion by an Intraductal Papillary Mucinous Neoplasm of Pancreas: A Case Report of an Unusual and Unreported High-Risk Feature of Malignant Progression.

Perineural invasion is a frequent histological finding in pancreatic adenocarcinoma. However, perineural invasion by intraductal papillary mucinous neoplasm (IPMN), a precursor lesion of pancreatic adenocarcinoma, has not been reported so far. We report a unique case of perineural invasion by IPMN in a 60-year-old female who underwent pancreatoduodenectomy for high-risk features of IPMN. Histological evaluation showed increased nerve density in the connective tissue of IPMN with multiple foci of perineural invasion by IPMN. In addition, there was a discrete 2 mm focus of invasive carcinoma that did not show perineural invasion. Chemotherapy was started and the patient is disease-free at 29 months follow up. The case illustrates previously unreported neuroplastic alterations and neutrotropism in benign neoplastic component of a malignant IPMN.