VGLL-fused intraparenchymal schwannoma with EWSR1::VGLL1 fusion: integrated clinicopathological and molecular characterization.

Intraparenchymal schwannomas are rare intracranial tumors confined to the brain parenchyma without connection to peripheral nerves. While conventional schwannomas are often associated with NF2 inactivation, the pathogenesis of intraparenchymal schwannomas remains poorly understood. Recent molecular studies have identified a distinct subgroup characterized by VGLL family fusions, suggesting a unique pathogenetic mechanism. Here, we report a 24-year-old woman presenting with dizziness and facial palsy who underwent resection of a brainstem tumor that showed histopathological features consistent with schwannoma. DNA methylation profiling classified the tumor as a VGLL-fused schwannoma, and RNA sequencing identified an EWSR1::VGLL1 fusion with markedly higher VGLL1 mRNA expression compared to a reference cohort of 17 vestibular schwannomas. Copy number analysis revealed loss of chromosome 19 without loss of chromosome 22q. These findings support a potential role for VGLL1 fusion in the pathogenesis of this rare tumor subtype. Importantly, this case further substantiates the emerging molecular subset of VGLL-fused intraparenchymal schwannomas and underscores the value of integrated molecular and histopathological analyses in the classification of central nervous system tumors.