After a biopsy or surgery to remove the tumor, a pathologist examines the cells of the brain tumor under a microscope and determines the tumor's grade. The tumor grade is an indication of the way the cells can grow. This information helps doctors plan the most suitable treatment.

Grades 1 and 2

These tumors are usually called low-grade or benign. They grow slowly.

Grades 3 and 4

These tumors are called high-grade or malignant. They grow more quickly.