Atypical meningiomas compared to other WHO Grade 2 meningiomas: Histological features and prognosis.

Objectives: To study each atypical feature in atypical meningioma versus other grade 2 meningiomas and its possible relation to recurrence.

Methods: This is a retrospective study of patients with WHO grade 2 meningioma operated in our institution between 01/2008 and 12/2020. The rate of recurrence, reoperation and readmission were recorded during the follow-up period. A statistical analysis was done to determine the significance of each pathological feature in regard to recurrence.

Results: A total of 74 patients were included as WHO grade 2 meningioma with 60 (81%) patients having an AM and 14 (19%) patients with chordoid or clear cell meningioma. The mean age was 51 years±14. The most common location was meningioma abutting the frontal lobe (convexity). Major atypical features were more noted in the AM, however, there was no significant difference between AM and other types of meningioma. Increased Nuclear cytoplasmic ratio and cellularity were found significantly more in AM. The recurrence rate was 16.2%. No specific pathology feature (major or minor) nor the type of Grade 2 meningioma was significantly related to recurrence.

Conclusion: The types of WHO grade 2 meningiomas have similar prognosis and recurrence rates. There is no significant difference between the atypical features in indicating a more aggressive nature or risk of recurrence in grade 2 meningiomas.