1. Clinic of Pediatrics Dortmund Municipal Hospital Dortmund Germany
2. SIREDO Oncology Center (Care, Innovation and Research for Children, Adolescents and Young Adults with Cancer), Institut Curie PSL University Paris France
3. PediatricHematology Unit Kaplan Medical Center Rehovot Israel
4. Department of Pediatrics, Hematology and Oncology Medical University Gdansk Poland
5. Clinic of Pediatric Hematology and Oncology University of Padova Padua Italy
6. Clinic of Pediatric Hematology and Oncology University of Tübingen Tübingen Germany
7. Clinic of Pediatric Surgery University of Padova Padua Italy
8. Istituto Tumori Milan Italy
9. Department of Pediatric Surgery, Marciniak Hospital, Department of Pediatric Traumatology and Emergency Medicine Medical University Wroclaw Poland
10. Department of Hematology and Oncology University Children's Hospital, University of Belgrade Belgrade Serbia
11. Pediatric Hematology Oncology Department Hospital Universitario de Cruces Barakaldo‐Bizkaia Spain
12. Pediatric Oncology Unit Aglaia Kyriakou Children's Hospital Athens Greece
13. Department of Pediatrics, Clinical Hospital Center Rijeka University of Rijeka Rijeka Croatia
14. International Ovarian and Testicular Stromal Tumor Registry Cancer and Blood Disorders, Children's Minnesota Minneapolis Minnesota USA
15. Gustave Roussy, Department of Pediatric Oncology Université Paris‐Saclay Villejuif France
16. Paris‐Saclay University, Paris‐Sud University Paris France