Diagnostic and prognostic significance of immunohistochemistry in pancreatic tumors

Aim The aim of this study was to reveal better immunohistochemical diagnostic markers for differentiating solid pseudopapillary neoplasm (SPN) from neuroendocrine tumor (NET) and pancreatic ductal adenocarcinoma (PDAC) and examine their prognostic significance in pancreatic tumors. Patients and methods We reviewed 55 pancreatic surgical specimens of SPN (10 cases), NET (15 cases), and PDAC (30 cases). We carried out comprehensive immunohistochemical profiling using three markers: CD99, E-cadherin, and claudin-5. Results In SPN, 90% (9/10) of the cases displayed paranuclear dot-like immunoreactivity for CD99; in contrast, 100% (15/15) of the cases of pancreatic NET displayed membranous staining, and 96.7% (29/30) of PDAC showed no expression of it ( P <0.01). Membranous claudin-5 expression was observed in all cases of SPN but was absent in 93.3% (14/15) cases of pancreatic NET, and 46.4% of PDAC cases. The difference was significant ( P <0.05). There was a statistically significant correlation between the expression of claudin-5 and CD99 in SPN ( P =0.456). Severe loss of membranous expression of E-cadherin was detected in 100% (10/10) of SPN cases, 100% of NET (15/15) showed intact and mild loss of E-cadherin, and 70% (21/30) of PDACs showed intact and mild loss of E-cadherin ( P <0.05). There was a statistically significant correlation between the expression of E-cadherin and CD99 ( P =0.604), and between E-cadherin and claudin-5 ( P =0.885) in SPN. Loss of E-cadherin expression was observed in 45% (9/20) of well differentiated and moderately differentiated adenocarcinoma and all the 10 (100%) cases of poorly differentiated adenocarcinoma ( P <0.05). Conclusion Our findings demonstrated that the pattern of CD99 expression was highly specific for distinguishing solid pseudopapillary tumors from other pancreatic tumors. CD99 combined with E-cadherin and claudin-5 can be used as a relatively specific expression profile of solid pseudopapillary tumors. Loss of E-cadherin expression may be a late event in pancreatic cancer progression.