Atypical Meningioma – Mitoses and Macronucleoli

The vast majority of meningiomas are benign grade I tumors.  Meningiomas can be upgraded to grade II, called atypical meningiomas, if they show increased mitotic activity (4 or more mitoses in 10 high power fields) or other worrisome histopathologic features, such as tumor cells exhibiting a prominent and large nucleolus.  Notice the mitosis in the center-right of the image and prominent nucleoli n the tumor cells comprising this atypical meningioma.