Solid-pseudopapillary neoplasms (SPNs) of the pancreas are uncommon and occur preferentially in young women. The question whether the features of SPNs occurring in men differ from those in women has not yet been studied. For a better understanding of the clinicopathological features of SPNs of both sexes, we studied a series of 14 tumors surgically resected at a Japanese hospital within a period of 14 years. This series was composed of seven men and seven women. All these SPNs demonstrated nuclear and cytoplasmic accumulation of β-catenin protein in immunohistochemistry and 86% of them had activating mutations of β-catenin gene. No pancreatic neuroendocrine tumors showed such immunohistochemical findings and genetic alterations. In our series, most SPNs in women showed encapsulation by thick fibrous tissue and massive degenerative changes. Most SPNs in men exhibited solid components without prominent degenerative changes, even though they were of a similar size to those in women. These findings suggest that SPNs in men tend to be a solid mass with slower progression of degenerative changes during their growth compared to that in women. Nuclear accumulation of β-catenin appears to be a useful marker of SPN, which allows male SPNs to be correctly diagnosed despite their less typical features.
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