1. Department of Pediatric Oncology, Hospital Sant Joan de Déu, Barcelona, Spain
2. Department of Pediatrics, Memorial Sloan–Kettering Cancer Center, New York, NY, USA
3. Department of Pathology, Hospital Virgen del Rocío, Sevilla, Spain
4. Sarcoma Research Group, Institut d’Investigació Biomèdica de Bellvitge, Barcelona, Spain
5. Department of Surgery, Memorial Sloan–Kettering Cancer Center, New York, NY, USA
6. Department of Pathology, Memorial Sloan–Kettering Cancer Center, New York, NY, USA
7. Centro Consulenze Anatomia Patologica Oncologica, Milano, Italy