1. Department of Paediatric Oncology, University of Edinburgh, Royal Hospital for Sick Children, Sciennes Road, Edinburgh EH9 1LW, UK.
2. Orthopaedic Department, University of Edinburgh, New Royal Infirmary, Old Dalkeith Road, Edinburgh EH16 4SU, UK.
3. Department of Pathology, University of Glasgow, Western Infirmary, Dumbarton Road, Glasgow G11 6NT, UK.