Pancreatic neuroendocrine tumor and solid-pseudopapillary neoplasm: Key immunohistochemical profiles for differential diagnosis

AIM: To reveal better diagnostic markers for differentiating neuroendocrine tumor (NET) from solid-pseudopapillary neoplasm (SPN), focusing primarily on immunohistochemical analysis. METHODS: We reviewed 30 pancreatic surgical specimens of NET (24 cases) and SPN (6 cases). We carried out comprehensive immunohistochemical profiling using 9 markers: Synaptophysin, chromogranin A, pan-cytokeratin, E-cadherin, progesterone receptor, vimentin, α-1-antitrypsin, CD10, and β-catenin. RESULTS: E-cadherin staining in NETs, and nuclear labeling of β-catenin in SPNs were the most sensitive and specific markers. Dot-like staining of chromogranin A might indicate the possibility of SPNs rather than NETs. The other six markers were not useful because their expression overlapped widely between NETs and SPNs. Moreover, two cases that had been initially diagnosed as NETs on the basis of their morphological features, demonstrated SPN-like immunohistochemical profiles. Careful diagnosis is crucial as we actually found two confusing cases showing disagreement between the tumor morphology and immunohistochemical profiles. CONCLUSION: E-cadherin, chromogranin A, and β-catenin were the most useful markers which should be employed for differentiating between NET and SPN.