A case of sclerosing variant of pancreatic neuroendocrine tumour with mucin lakes.

Sclerosing variant of pancreatic neuroendocrine tumour is a subtype of pancreatic neuroendocrine tumours with abundant fibrous stroma. Sclerosing variant of pancreatic neuroendocrine tumours clinically and radiologically mimic ductal carcinoma and have been reported to have a possible poor prognosis. Here, we describe a case of the sclerosing variant of pancreatic neuroendocrine tumour with mucin lake formation. In the current case, the duct component was intimately incorporated into the neuroendocrine tumour nests; these observations together with the invasive proliferation required differentiation from mixed neuroendocrine-non-neuroendocrine neoplasm and ductulo-insular variant of pancreatic neuroendocrine tumours. Detailed observation clarified that the ducts in the tumour were entrapped in normal pancreatic ducts. Moreover, the current case was a pseudoglandular variant of pancreatic neuroendocrine tumours. The tumour cells produced a small amount of mucin, degenerated, and shed to form mucin lakes. This is a unique and peculiar morphology of pancreatic neuroendocrine tumours and is reported here as a notable case.