Meningiomas constitute about 20% of intracranial tumors. They are derived from the arachnoid cells and are mixed epithelial-mesenchymal. They are extracerebral. As can be seen from this photograph, they lie outside brain and do not invade the brain parenchyma. They are always attached to the dura.
In spite of their benign histologically appearance, they can still act as space occupying lesion and cause considerable squashing and distortion of the brain.