1. Department of Pediatric Pathology; Kiel Pediatric Tumor Registry, Christian-Albrechts-University Kiel; Kiel Germany
2. Department of Pediatric Hematology and Oncology; University Medical Center Hamburg-Eppendorf; Hamburg Germany
3. Department of Pediatric Surgery; Dr. von Hauner Children's Hospital, Ludwig-Maximilians-University Munich; Munich Germany