WHO grade 1 meningiomas, with 10-year progression free survival rates >70%, are pretty benign, right? This large international cohort study demonstrated grade 1 tumors with loss of chromosome 1p were on par with grade 2 tumors with a median PFS of 4.5 years. Those with both loss of 1p and gain of 1q were on par with grade 3 tumors with a median PFS of 2.2 years.The authors thus argue for 1p loss to define grade 2 and 1q gain to define grade 3, which would upgrade 10% of this cohort: 13% grade 1→2, 0.7% grade 1→3, and 4.4% grade 2→3. This is particularly useful given chromosome-level alterations can be detected with readily available technology such as fluorescence in situ hybridization. | Landry, JAMA Oncol 2025
