Pancreatic intraductal papillary-mucinous neoplasms: a new and evolving entity

Abstract

For a long time, intraductal tumors of the pancreas were neglected because they were misdiagnosed as mucinous cystadenocarcinoma, ordinary ductal adenocarcinoma, or chronic pancreatitis. Only in recent years have they been recognized as clinical and pathological entities. Most common are the intraductal papillary-mucinous neoplasms. Although they show an adenoma-carcinoma sequence, they have proved to have a more favorable prognosis than ductal adenocarcinoma, when resected in a preinvasive state. Recently, it has become clear that they constitute a heterogeneous group with at least four subtypes. Their stratification reveals that the various intraductal papillary-mucinous neoplasm subtypes have different biological properties with different prognostic implications.

Fig. 1

Histological subtypes of intraductal papillary-mucinous neoplasms of the pancreas and their usual mucin pattern. a, b IPMN of the intestinal type positive for MUC2; c, d IPMN of the pancreatobiliary type positive for MUC1; e, f IPMN of the oncocytic type showing scattered positivity for MUC2; g, h IPMN of the gastric type, positive for MUC5

Fig. 2

IPMN of the gastric type showing severe cellular atypia and MUC5 positivity

Fig. 3

PanIN-1 lesion associated with lobular fibrosis

Fig. 4

Small multicystic duct-associated lesion in the periphery of pancreatic tissue suggestive of an IPMN of the gastric type but difficult to distinguish from a large PanIN-1 lesion