Serous cystic neoplasms of the pancreas: an immunohistochemical analysis revealing alpha-inhibin, neuron-specific enolase, and MUC6 as new markers.

Serous cystic neoplasms (SCNs) of the pancreas include serous microcystic adenoma (SMA), serous oligocystic ill-demarcated adenoma (SOIA), solid serous adenoma (SSA), von Hippel-Lindau-associated cystic neoplasm (VHL-CN), and serous cystadenocarcinoma (SCC). These neoplasms are histologically similar but differ in their localization, gross appearance, gender distribution, and biology. A centroacinar origin is assumed but has not been proven. To clarify whether the various subtypes of SCN may be distinguished from each other by marker profiles that might also provide evidence of their origin, the immunoprofiles of 38 SCNs (21 SMAs, 13 SOIAs, 2 VHL-CNs, 1 SSA, and 1 SCC) were defined by applying antibodies against cytoskeletal, neuroendocrine, hormone receptor, and mucin markers. In addition, we examined the expression of calretinin and alpha-inhibin. The various types of SCN showed a very similar immunoprofile, characterized by positivity for cytokeratins and neuron-specific enolase and negativity for vimentin and synaptophysin. Further markers that were commonly expressed in SCNs were alpha-inhibin (SMAs: 76%, SOIAs: 92%, VHL-CNs: 100%), MUC6 (SMAs: 60%, SOIAs: 85%, VHL-CNs: 100%), and MUC1 (SMAs: 24%, SOIAs: 38%, VHL-CNs: 50%). Western blot analysis in one SMA revealed a distinct band that stained with neuron-specific enolase antiserum. Alpha-inhibin was only expressed in 4 of 11 acinar cell carcinomas and not in five ductal adenocarcinomas, five neuroendocrine tumors, one mixed ductal-endocrine carcinoma, and one acinar cell cystadenoma of the pancreas. These results suggest that, despite their biologic differences, the various types of SCNs are composed of the same (or a very similar) cell type and may therefore have a common direction of differentiation. This notion is further supported by the finding that neuron-specific enolase, alpha-inhibin, and MUC6, which may be regarded as new markers for this pancreatic tumor type, were also expressed in most SCNs. Because a number of SCNs share MUC1 and MUC6 expression with the pancreatic centroacinar cells, the possibility of a histogenetic relationship has to be considered.