4 Pediatric Department, Faculty of Medicine and Nursing, University of the Basque Country, UPV/EHU, Leioa, Spain.
5 Department of Hemato-oncology, Princess Maxima Center for Pediatric Oncology, Utrecht, The Netherlands.
6 Centre de Référence des Histiocytoses Registre des histiocytoses, Service d'Hémato-Oncologie Pédiatrique Hopital Trousseau APHP Paris Sorbonne, Paris, France.
7 Childhood Cancer Research Unit, Department of Women's and Children's Health, Karolinska Institute, Stockholm, Sweden.
8 Department of Pediatrics, Astrid Lindgrens Children's Hospital, Karolinska University Hospital, Stockholm, Sweden.
9 Pediatric Hematology Oncology, University Hospital Leuven, Leuven, Belgium.
10 Department of Pediatrics, Division of Hematology, Oncology and Hemostaseology, Goethe University Frankfurt, Frankfurt/Main, Germany.
11 Pediatric Department of Oncology and Hematology, Oslo University Hospital, Oslo, Norway.
12 Department of Paediatrics, Watford General Hospital, Watford, UK.
13 Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK.
14 Department of Paediatrics and Adolescent Medicine, Copenhagen University Hospital - Rigshospitalet, Copenhagen, Denmark.
15 Children's Health Ireland at Crumlin, Dublin, Ireland.
16 Department of Oncology and Surgical Oncology for Children and Youth, Institute of Mother and Child, Warsaw, Poland.
17 Pediatric Hematology/Oncology Department, Meyer Children's University Hospital, Florence, Italy.
18 Department of Pediatric Hematology and Oncology, Charles University in Prague, 2nd Faculty of Medicine and Motol University Hospital, Prague, Czech Republic.
19 CCRI, St. Anna Kinderkrebsforschung, Vienna, Austria.
20 Faculty of Medicine, Sigmund Freud Private University, Vienna, Austria.