Molecular Characterization of Metanephric Adenomas Beyond BRAF: Genetic Evidence for Potential Malignant Evolution

AIMS: Metanephric adenomas (MA) are conventionally regarded as rare renal tumors with indolent behavior; limited case reports describe MA with aggressive features. Conventional MA harbor hotspot BRAF V600E mutations. A BRAF V600E senescence pathway, mediated by CDKN2A/p16, has been proposed to confer MA benignity. Aside from BRAF, the molecular landscape in both conventional MA and those with aggressive features has not been fully characterized. In this study we molecularly profiled a series of MA to investigate the correlation between genomic findings and clinical outcome. METHODS AND RESULTS: We retrospectively examined the histomorphology and patient outcomes of 11 conventional MA and one MA with aggressive features. Each was subjected to capture-based next-generation DNA sequencing of 479 cancer-related genes and immunohistochemical profiling. All tumors were positive for WT1 immunostaining and BRAF V600E mutation. One conventional MA contained an additional somatic BRCA2 pathogenic mutation. The MA with aggressive features showed a biphasic appearance: one component was epithelial with areas morphologically consistent with conventional MA; the second component was sarcomatous with areas of solid and angiosarcomatous growth. Differential profiling of the two populations revealed identical BRAF, EIF1AX, and TERT promoter hotspot mutations in the epithelial and sarcomatous components. Deep deletion of CDKN2A and MYC amplification were identified only in the sarcomatous component. CONCLUSIONS: While the vast majority of MA show indolent behavior, rare pathogenic alterations can occur in conventional MA in addition to BRAF. Molecular profiling of a case with aggressive clinical and pathologic features shows genetic evidence for malignant evolution in MA.