Solid Pseudopapillary Tumor : Molecular Genetics
Molecular Genetics: The histogenesis of solid pseudopapillary tumor (SPT) of pancreas is uncertain; however, it involves activation of Wnt/β-catenin pathway. Almost 90% of cases have point mutations in exon 3 of the CTNNB1 gene (which encodes β-catenin). This gain of function mutation prevents β-catenin degradation resulting in its nuclear accumulation (which can be demonstrated immunohistochemically).
β-catenin forms complexes with lymphoid enhancer-binding factor 1 (LEF1)/T-cell factor transcription complex in the nucleus. Interaction between β-catenin and LEF1 activates Wnt/β-catenin pathway which is associated with upregulation of several genes in Notch, hedgehog, and androgen receptor signaling pathways leading to tumorigenesis.
The image shows solid areas in a SPT with aggregates of foamy histiocytes. Occasionally, giant-cell reaction to cholesterol crystals can be seen. Mitoses are usually rare.