Psammoma bodies in meningioma, light micrograph. A meningioma is a slow-growing tumour that is usually benign (non-cancerous) and derived from the meninges (membranes around the brain). It is the most common primary intracranial tumour in adults. Histologically, meningioma cells are relatively uniform, with a tendency to encircle one another, forming whorls and psammoma bodies, which are concentric laminated eosinophilic bodies that tend to calcify. Depending on the location and size the tumour can generate symptoms by pressing on nearby tissue.