Most common primary brain tumor (20-30% of brain tumors, 6 per 100K annually)
Derive from arachnoid cap cells (associated with dura mater, choroid plexus)
Grow along external surface of brain or within ventricular system
Slow growing (may grow rapidly during pregnancy), symptoms vague or related to brain compression
Usually adults
Female predominance: 2/3 of cerebral meningiomas occur in women, 90% of spinal cord meningiomas occur in women
Usually solitary; multiple tumors (seen in 1-6%) are occasionally associated with neurofibromatosis 2
Three grades exist based on WHO criteria
Most are WHO Grade I (benign)
~6% are WHO Grade II (increased likelihood of recurrence)
Rarely are WHO Grade III (malignant with metastatic potential)
Many variants of meningiomas exist