False-colour computed tomography (CT) brain scan showing a large, intracranial tumour, the large round mass (coloured purple) in centre. Within the tumour, spots indicate fluid-filled cysts. The outer border of the tumour (pale yellow) is calcified, which indicates a great age. This tumour is most probably a low-grade glioma, a tumour of the supporting glial cells, the specialised connective tissue of the brain and central nervous system. Gliomas include the astrocytomas & glioblastomas and account for the majority of intracranial tumours. Slow-growing, low-grade (less malignant) gliomas may become transformed into more malignant forms in time.