How serious a meningioma is depends on its grade and location.
How meningiomas are graded:
The grade (I to III) of a meningioma is based on the tumor cells’ appearance under a microscope. Grade I is the most common and benign, and grade III is the most aggressive and is considered malignant.
There are three main grades (classifications) of meningiomas:
- Grade I – Benign meningioma: This non-cancerous type of brain tumor grows slowly and has distinct borders. Approximately 78-81% of meningiomas are benign (non-cancerous).
- Grade II – Atypical meningioma: Approximately 15-20% of meningiomas are atypical, meaning that the tumor cells do not appear typical or normal. Atypical meningiomas are neither malignant (cancerous) nor benign, but may become malignant. Grade II atypical meningiomas also tend to recur and grow faster.
- Grade III – Malignant or anaplastic meningioma: Malignant or anaplastic meningioma is an aggressive type of brain tumor that tends to invade the parts of the brain nearest to the tumor. Approximately 1-4% of meningiomas are grade III (cancerous).