1. From the St Anna Children's Hospital; Departments of Pathology and Orthopedics, University Hospital Vienna, Vienna, Austria; Department of Orthopedics, University Hospital Zürich, Zürich, Switzerland; Diagnostic Radiology, Hamburg; Department of Nuclear Medicine, University Hospital Muenster; Department of Pediatric Hematology and Oncology, University Children's Hospital Muenster, Muenster; and Olgahospital, Pediatrics 5–Oncology, Hematology, Immunology, Stuttgart, Germany