1. Department of Pediatric Hematology‐Oncology (TAO) Marianna V Vardinoyannis‐ELPIDA Oncology Unit Agia Sofia Children's Hospital Athens Greece
2. Pediatric Oncology Group Biocruces Bizkaia Health Research Institute Barakaldo Spain
3. Pediatric Department Hospital Universitario Cruces, Osakidetza Barakaldo Biscay Spain
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