Site-Specific Genomic Alterations in a Well-Differentiated Pancreatic Neuroendocrine Tumor With High-Grade Progression

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The major categories of pancreatic neuroendocrine tumor (PanNET) are well-differentiated NET and poorly differentiated neuroendocrine carcinoma. Sequencing of these tumors has identified multiple important genes in the pathogenesis of PanNETs, such as DAXX/ATRX, MEN1, TP53, RB, and mTOR pathway genes. We identified a case of well-differentiated PanNET with high-grade progression with simultaneous low- and high-grade histologic regions containing variable genomic profiles. We performed tumor microdissection and analyzed both regions using a 409-gene comprehensive cancer panel using next-generation sequencing in addition to immunohistochemical and morphologic studies. The low-grade region showed a change in the DAXX gene as a copy number variant (CNV) deletion. The high-grade region showed CNV deletion changes in the DAXX gene as well as the MEN1 gene. We observed additional mutational changes in the PTEN gene and SMAD4 gene in the high-grade region. Our data support that high-grade progression in PanNETs may be the result of the progressive accumulation of genetic changes (CNVs and point mutational changes) within the body of the tumor. Next generation sequencing may provide pathologists and clinicians with ancillary information to accurately characterize and treat these tumors.

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