A rare case of supratentorial ependymosarcoma harboring ZFTA::RELA fusion.

Ependymosarcoma is an exceedingly rare variant of ependymoma characterized by a mixture of ependymomatous and sarcomatous components. We report a case of supratentorial ependymosarcoma harboring a ZFTA::RELA fusion in a 10-year-old girl. Histologically, the tumor comprised an ependymomatous component resembling clear cell ependymoma and a sarcomatous component. ZFTA::RELA fusion was confirmed in both components. Genome-wide methylation profiling classified both components as supratentorial ependymoma, ZFTA fusion-positive by the German Cancer Research Center (DKFZ) CNS tumor classifier v12b8. However, their copy number alteration profiles were distinct. The ependymomatous component exhibited a gain of chromosome 1q and a loss of chromosomes 1p, 9, and 19q, while the sarcomatous component showed a loss of chromosome 14. These findings suggest that both components may have differentiated from a common precursor despite their distinct morphologies. The patient underwent gross total resection followed by adjuvant chemoradiotherapy and remains recurrence-free eight years post-treatment. Further investigation of additional cases is warranted to better understand the pathogenesis of this rare tumor.