Poorly differentiated endocrine carcinoma and intraductal papillary-mucinous neoplasm of the pancreas: Description of an unusual case.

Neuroendocrine tumors and intraductal papillary-mucinous neoplasms constitute histologically distinctive but relatively rare entities among pancreatic tumors. Collision of these tumors is extremely rare and causes several diagnostic problems regarding the histopathologic differential diagnosis of other pancreatic epithelial tumors. The question of whether the neoplastic populations originate from common progenitor cell or whether they represent only a fortuitous association has not been sufficiently explained. Here, we describe a new case of poorly differentiated endocrine carcinoma combined with an intraductal papillary-mucinous neoplasm. To disclose the relationship between the two histologic components, neuroendocrine differentiation was studied by confocal laser scanning microscopy using double immunofluorescence labeling with chromogranin-A and CD57 antibodies. Our results revealed a co-localization of both antigens in neuroendocrine cells of the intraductal papillary-mucinous neoplasm. The finding has previously been described in non-neoplastic neuroendocrine cells. Cells forming poorly differentiated endocrine carcinoma showed a wide heterogeneity in immunoreactions. Our results do not indicate a potential histogenetic similarity between these two neoplasms, which are dissimilar histologically, and underline the previous thesis that cells in intraductal papillary-mucinous neoplasm revealing neuroendocrine differentiation represent only a non-neoplastic cell admixture.