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 a 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 < .0001) and symptom-free survival (P = .0007). Most meningiomas were molecularly low risk, although those from the hypermitotic DNA methylation group had higher IMPACT scores (P = .0020). Incidental meningiomas had distinct CNA and gene expression patterns and favorable outcomes compared to 1434 nonincidental meningiomas. CONCLUSIONS: These findings support surveillance for most incidental meningiomas, but early treatment may improve outcomes for molecularly higher-risk cases.