The most common type of brain tumor, meningioma, grows from the membranes surrounding the brain and spinal cord.
Usually they are benign, which means they are not cancerous.
However, a subset of meningiomas behave aggressively, recur rapidly despite surgery and radiation, and often cause death.
To guess whether a tumor will be benign or malignant, pathologists typically examine a surgically removed sample of a tumor under the microscope and look for irregular cell shape, accelerated cell division, and other tell-tale signs of cancer.
But the eyeball test doesn’t always work.
