The prognostic significance of clinicopathological features in meningiomas: Microscopic brain invasion can predict patient outcome in otherwise benign meningiomas

Abstract

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°I) or atypical meningioma WHO grade II (M°II) from Hannover Medical School and the other including atypical meningiomas defined according to the classical WHO criteria (M°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°I and 65 M°II patients with the latter group consisting of 25 patients with otherwise benign meningiomas with BI (M°IIa) and 40 with M°IIb. Results A significant difference of progression‐free interval (PFI) was found between patients with M°I and M°II, M°I and M°IIa and those with M°I and M°IIb of both cohorts and each separately. However, PFI of M°IIa and M°IIb patients showed no significant difference. In the multivariate regression analysis adjusted for M°I/M°IIa versus M°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.

Standardisation of canine meningioma grading: Inter‐observer agreement and recommendations for reproducible histopathologic criteria

“…Discerning the presence/absence of a layer of fusiform meningeal cells around the tumour could be challenging, especially in dogs where specific canine meningeal markers are lacking. Since tumour invasion into the central nervous system is associated with reactive astrocytosis, 29 in human medicine, GFAP‐staining is recommended to assess the presence of an astrocytic reaction on the invasive front 25,27,31,33 . However, the authors think that while helpful, astrocytosis should not be considered a sufficient parameter to assess invasion, since it can be observed in response to other stimuli, like tumour compression and perilesional edema.…”

Brain Invasion in Meningioma—A Prognostic Potential Worth Exploring

“…In a retrospective multicenter analysis of 200 atypical meningiomas that were treated with gross total resection, brain invasion was not associated with an increased risk of recurrence [37]. In contrast, a recent bi-institutional study compared 25 otherwise benign meningiomas and 40 atypical brain invasive meningiomas and identified brain invasion as an independent prognostic factor for the progression-free interval [38].…”

Increased proliferation is associated with CNS invasion in meningiomas

“…Besides the long-established histopathological assessment according to the WHO classification of central nervous system tumors [4], the detection of infiltrative meningioma growth into brain parenchyma has been added as a stand-alone criterion for atypia [4]. However, its prognostic significance has since been questioned based on contradictory results of retrospective analyses [6][7][8][9] and its role for tumor grading in the WHO classification is frequently discussed [10,11].…”

“…The mentioned retrospective studies that investigated the role of CNS invasion in meningiomas have focused on tumor recurrence as an outcome variable [6][7][8][9]. To our knowledge, there has been no detailed analysis of the proliferative activity in meningiomas with histopathological features of infiltrative growth.…”