How Meningiomas Are Graded

Physicians use grading to help tell how severe the tumor is. The tumor’s grade depends on what its cells look like under a microscope compared to healthy cells.

  • Grade I. Grade I tumors are not cancerous (benign). These tumors grow slowly and have clear borders. These are the most common type of meningiomas. About 78% to 81% of meningiomas are grade I.
  • Grade II. These tumors are atypical. This means their cells do not look normal. They tend to grow fast and come back. These tumors are not considered benign nor malignant. But, they can become cancerous in time. Around 15% to 20% of tumors fall in this category.
  • Grade III. Grade III is the most severe form. They are cancerous (malignant) tumors. They often invade areas of the brain near the tumor. About 1% to 4% percent of all meningiomas are grade III.