The Prognostic Significance Of Clinicopathological Features In Meningiomas: Microscopic Brain Invasion Can Predict Patient Outcome In Otherwise Benign Meningiomas

Aims Brain invasion (BI) was firstly defined as a single criterion of atypia in otherwise benign meningiomas in the revised fourth edition of 2016 WHO classification of brain tumours after being previously inconsistently addressed. However, recent studies have raised doubts about the prognostic significance of BI in otherwise benign meningiomas. In our study, we investigate the reproducibility of such a prognostic effect.Methods We identified two cohorts one consisting of 483 patients with meningioma WHO grade I (M degrees I) or atypical meningioma WHO grade II (M degrees II) from Hannover Medical School and the other including atypical meningiomas defined according to the classical WHO criteria (M degrees IIb) from the University Hospital Heidelberg. Follow-up data with a median observation time of 38.2 months were available from 308 cases. These included 243 M degrees I and 65 M degrees II patients with the latter group consisting of 25 patients with otherwise benign meningiomas with BI (M degrees IIa) and 40 with M degrees IIb.Results A significant difference of progression-free interval (PFI) was found between patients with M degrees I and M degrees II, M degrees I and M degrees IIa and those with M degrees I and M degrees IIb of both cohorts and each separately. However, PFI of M degrees IIa and M degrees IIb patients showed no significant difference. In the multivariate regression analysis adjusted for M degrees I/M degrees IIa versus M degrees IIb, sex, age, extent of resection and tumour location, BI exhibited the strongest risk of relapse (Hazard ratio: 4.95) serving as an independent predictor of PFI (p = 0.002).Conclusions Our results clearly support the definition of BI as a single criterion of atypia in WHO classification of 2016.