Solid Pseudopapillary Tumor : β-catenin & LEF1
Almost 90% of solid pseudopapillary tumors (SPT) of pancreas have point mutations in exon 3 of CTNNB1 gene resulting in nuclear accumulation of β-catenin which can be demonstrated immunohistochemically (as shown in this image). CTNNB1 is a central component of the Wnt signaling pathway and mediates gene expression through lymphoid enhancer-binding factor 1 (LEF1). Studies have shown strong nuclear reactivity for LEF1 in SPT of pancreas. The surrounding uninvolved pancreatic parenchyma is devoid of any LEF1 staining. Nuclear expression of both β-catenin and LEF1 has also been noted in pancreatoblastomas; however, the staining is localized within and around squamoid corpuscles. High-grade neuroendocrine carcinomas, pancreatic ductal adenocarcinomas, and acinar cell carcinomas are negative for both markers.