[1] North Bristol NHS Trust Bristol, Dept Neuropathol, Frenchay Hosp, Bristol, Avon, England
[2] North Bristol NHS Trust Bristol, Brain Tumour Res Grp, Frenchay Hosp, Bristol, Avon, England
[3] North Bristol NHS Trust, Bristol Genet Lab, Southmead Hosp, Bristol, Avon, England
[4] Univ W England, Dept Biostat, Bristol BS16 1QY, Avon, England
[5] Bristol Haematol & Oncol Ctr, Dept Neurooncol, Bristol, Avon, England