Meningioma, light micrograph. Meningioma is a slow-growing tumour usually benign derived from the meninges. 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, concentric laminated eosinophilic bodies that tend to calcify. Depending on the location and size the tumour can generate symptoms by pressing on nearby tissue.