DISTINCTIVE FEATURES

These tumors occur during adult life.
They occur more commonly in females in the cranium (3:2) and the spinal cord (10:1).
These tumors arise from the meningoepithelial cells of the arachnoid.
Grossly appear as round, firm, well defined, dural masse(s) without evidence of hemorrahge or necrosis. The tumor compresses the underlying brain tissue.
Microscopically the tumor exhibits various patterns.

Fibroblastic type consists of spindle cells with a collagenous stroma.
Syncytial type consists of clusters of tightly grouped cells with a syncytial pattern of growth.
Transitional type has the features of both fibroblastic and syncytial types.
Psammomatous type are tumors which contain a large number of psammoma bodies.
Papillary type consists of pleomorphic cells which are arranged around fibrovascular cores.
Malignant meningiomas are rare and hard to diagnose based on the histologic apperance. These tumors may contain atypical cells, numerous mitosis, and infiltration of adjacent brain tissue.