Brain cancer. Coloured coronal magnetic resonance imaging (MRI) scan through the head of a 48 year old male patient with a glioblastoma (centre right), with surrounding oedema (fluid) that is compressing the left ventricle (at right). A glioblastoma is a particularly malignant brain cancer that arises from the supporting glial cells in the brain. Treatment is with a combination of surgery and radiotherapy, but the prognosis is poor.