Unveiling a genetic rarity: intracranial sarcomatous tumor with EWSR1::PATZ1 fusion-a case report and review of the literature.

PATZ1 fusion neuroepithelial tumors (NET) are beginning to be recognized as a distinct molecular class of neoplasms that most often occur in children and young adults. These tumors are polyphenotypic, show diverse morphologic features, may be low- or high-grade, and tend to have an intermediate prognosis. We present a rare case of a high-grade NET harboring an EWSR1::PATZ1 fusion, identified through DNA methylation profiling and validated by gene expression analysis. The case involved a 21-year-old female presenting with headaches and seizures. The tumor was supratentorial in close relation to the lateral ventricle, preferentially located in the parietal lobe. Morphologically it showed predominant sarcomatous morphology with high mitotic activity and a high Ki-67 index leading to its initial diagnosis of gliosarcoma. Awareness of the emerging entity of PATZ1 fusion NET is important not only for accurate diagnostic and prognostic purposes but also for predicting response to therapy.