1. Faculty of Medicine, University of Oslo, Oslo, Norway
2. Department of Neurosurgery, Oslo University Hospital, Ullevål, Oslo, Norway
3. Department of Pathology, Oslo University Hospital, Rikshospitalet, Oslo, Norway
4. The Norwegian Cancer Registry, Oslo, Norway
5. Department of Pathology, Oslo University Hospital, Ullevål, Oslo, Norway
6. Department of Neurosurgery, Oslo University Hospital, Rikshospitalet, Oslo, Norway