CNS Tumor with BCOR/BCORL1 Fusion: A Rare Tumor Entity.

Area of Science:

• Neuro-oncology
• Molecular Pathology
• Genomics

Background:

• Central nervous system (CNS) tumors with BCOR/BCORL1 gene fusions are exceptionally rare, with fewer than 40 reported cases.
• These tumors are distinct from CNS tumors with BCOR internal tandem duplication and even rarer are those lacking fusions but possessing BCOR truncating variants.

Observation:

• Diagnosis is challenging due to rarity and mimicry of oligodendrogliomas and ependymomas; Olig2 positivity with focal to absent GFAP may indicate this entity.
• A 37-year-old woman presented with a midline CNS tumor harboring a BCOR c.626del variant (p.S209Cfs*7) without a detectable fusion.
• Unusual focal strong dot-like perinuclear EMA immunoreactivity was observed, a feature not previously reported.

Findings:

• The patient with a BCOR variant (lacking fusion) achieved successful treatment with definitive radiation therapy and adjuvant temozolomide.
• This case adds to the limited evidence supporting radiation and temozolomide for CNS tumors within the BCOR/BCORL1 fusion methylation class but without a fusion.

Implications:

• This study expands the understanding of rare CNS tumors with BCOR alterations.
• It suggests a potential therapeutic approach involving radiation and temozolomide for CNS tumors with BCOR variants and no detectable fusion.
• Further research is warranted to establish standard treatment protocols for these rare entities.