Large solid-pseudopapillary neoplasm of the pancreas with aberrant protein expression and mutation of β-catenin: a case report and literature review of the distribution of β-catenin mutation.

Solid-pseudopapillary neoplasms (SPN) are rare pancreatic tumors. The etiology of SPN involves mutations in the gene that encodes β-catenin (CTNNB1). We herein report the case of a 23-year-old woman with a large SPN with proliferating tumor cells that displayed both solid and pseudo-papillary patterns. The simultaneous nuclear accumulation and loss of membrane localization of β-catenin and E-cadherin was specifically observed in the tumor cells. Further, the tumor cells were shown to harbor a missense mutation in exon 3 of CTNNB1. We also present a review of the literature describing the clustering of CTNNB1 mutations in patients with SPN.