Atypical Meningioma

Comments:
Atypical meningioma are WHO Grade II tumors. Two major criteria come into consideration in order to upgrade meningiomas; (1) Mitotic index (greater than or equal to 4/10 HPF); and (2) At least 3 of the 5 following parameters: sheeting architecture, small cell formation, hypercellularity, macronucleoli, spontaneous necrosis. This picture illustrates mitotic figures and sheeting architecture.