Incidental meningiomas have favorable clinical outcomes across molecular classification systems

Background Clinical and radiographic models predict incidental meningioma growth, but their molecular architecture is unknown. Methods We analyzed serial magnetic resonance imaging, IMPACT groups (Incidental Meningioma: Prognostic Analysis Using Patient Comorbidity and MRI Tests), targeted gene expression, DNA methylation, and copy number (CNA) profiling of 238 consecutive incidental meningiomas from a single neurosurgical center. Results The cohort was 81% female, with median age of 59 years at detection, and median tumor volume of 3.83 cm³. Symptoms developed in 15.5%; 93.7% were treated (median time-to-treatment 1.06 years), with 5% recurrence. IMPACT groups stratified treatment-free (p < 0.0001) and symptom-free survival (p = 0.0007). Most meningiomas were molecularly low risk, although those from the Hypermitotic DNA methylation group had higher IMPACT scores (p = 0.0020). Incidental meningiomas had distinct CNA and gene expression patterns and favorable outcomes compared to 1,434 non-incidental meningiomas. Conclusions These findings support surveillance for most incidental meningiomas, but early treatment may improve outcomes for molecularly higher risk cases.