Intraductal papillary-mucinous neoplasm of the pancreas: a report of five cases with immunohistochemical findings.

Five cases of intraductal papillary-mucinous neoplasm (IPMN) of the pancreas are here described. This group of tumors represents a distinct clinicopathological entity with characteristic endoscopic, radiological, gross and microscopic appearances. Our five cases all showed marked dilatation of the main pancreatic duct which contained mucin and papillary tumor, sometimes filling and sometimes lining the lumen. The papillae were lined by columnar epithelium showing varying degrees of dysplasia. In one case there was adjacent invasive adenocarcinoma. Immunohistochemical staining for p53 protein was strongly positive in a majority of cells in the three cases with severe epithelial dysplasia and in the invasive adenocarcinoma, while weaker staining in a minority of cells was seen in the remaining two cases. A small proportion of tumor cells expressed PCNA and Ki-67 immunohistochemically in four cases, while the case with severe dysplasia and invasive carcinoma showed positivity for these proliferation markers in most cells. The four cases of exclusively intraductal tumor showed no evidence of disease recurrence at follow-up (median 55 months). The patient with IPMN and associated invasive adenocarcinoma died 21 months post-operatively. In view of its relatively favourable prognosis, it is important that IPMN is recognised.