Neurocytomas are rare low-grade brain tumors predominantly affecting young adults, but their cellular origin and molecular pathogenesis is largely unknown. We previously reported a sellar neurocytoma that secreted excess arginine vasopressin causing syndrome of inappropriate anti-diuretic hormone (SIADH). Whole exome sequencing in 21 neurocytoma tumor tissues identified somatic mutations in the plant homeodomain finger protein 14 (PHF14) in 3/21 (14%) tumors. Of these mutations, two were missense mutations and 4 caused splicing site losses, resulting in PHF14 dysfunction. Employing shRNA-mediated knockdown and CRISPR/Cas9-based knockout approaches, we demonstrated that loss of PHF14 increased proliferation and colony formation in five different human, mouse and rat mesenchymal and differentiated cell lines. Additionally, we demonstrated that PHF14 depletion resulted in upregulation of platelet derived growth factor receptor-alpha (PDGFRα) mRNA and protein in neuroblastoma SHSY-5Y cells and led to increased sensitivity to treatment with the PDGFR inhibitor Sunitinib. Furthermore, in a neurocytoma primary culture harboring splicing loss PHF14 mutations, overexpression of wild-type PHF14 and sunitinib treatment inhibited cell proliferation. Nude mice, inoculated with PHF14 knockout SHSY-5Y cells developed earlier and larger tumors than control cell-inoculated mice and Sunitinib administration caused greater tumor suppression in mice harboring PHF-14 knockout than control SHSY-5Y cells. Altogether our studies identified mutations of PHF14 in 14% of neurocytomas, demonstrate it can serve as an alternative pathway for certain cancerous behavior, and suggest a potential role for Sunitinib treatment in some patients with residual/recurrent neurocytoma.

Central nervous system (CNS) tumor with BCL6 corepressor gene BCOR/BCORL1 fusion is an extremely rare tumor entity, with fewer than 40 cases reported. These tumors are distinct from the WHO 2021-defined CNS tumor with BCOR internal tandem duplication. Even rarer are CNS tumors that match to the methylation class of CNS tumors with BCOR/BCORL1 fusion, but lack fusions and instead harbor truncating small nucleotide variants in BCOR. To our knowledge, only two other cases of this scenario have been previously reported. Due to their scarcity and morphological features that mimic oligodendrogliomas and ependymomas, the diagnosis of CNS tumor with BCOR/BCORL1 fusion can be challenging, and misdiagnoses are not uncommon. Histologic findings of Olig2 positivity with focal to absent GFAP warrant further evaluation for this tumor entity. Moreover, no standard of care therapy exists for these tumors, making treatment selection difficult. We present a case of a 37-year-old woman with a midline CNS tumor with BCOR/BCORL1 fusion, harboring a pathogenic BCOR c.626del (p.S209Cfs*7) (Exon 4) variant, who was successfully treated with definitive radiation therapy and adjuvant temozolomide. Notably, EMA showed focal strong dot-like perinuclear immunoreactivity, which has not been previously reported in these tumors. This case adds to the limited but growing body of evidence supporting the use of radiation and temozolomide in treating tumors matching the methylation class of CNS tumors with BCOR/BCORL1 fusion without a detectable fusion.