You need to find 4 mitoses/10 HPF or brain invasion to call grade 2 (atypical) and 20 mitoses/10 HPF to call anaplastic (grade 3) meningiomas.
You need to find 4 mitoses/10 HPF or brain invasion to call grade 2 (atypical) and 20 mitoses/10 HPF to call anaplastic (grade 3) meningiomas.