1. Department of Surgical Oncology for Children and Youth; Institute of Mother and Child; Warsaw Poland
2. Department of Pediatric Hematology, Oncology and Bone Marrow Transplantation; Medical University of Lublin; Lublin Poland
3. Department and Clinic of Pediatric Oncology, Hematology and Bone Marrow Transplantation; Wroclaw Medical University; Wroclaw Poland
4. Unit of Pediatric Oncology, Hematology and Chemotherapy; Medical University of Silesia; Katowice Poland
5. Department of Pediatric Hematology and Oncology Collegium Medicum; Nicolaus Copernicus University; Bydgoszcz Poland
6. Department of Oncology and Hematology; University Children's Hospital of Kracow; Kracow Poland
7. Department of Pediatric Hematology and Oncology; Medical University of Gdansk; Gdansk Poland
8. Pediatric Oncology, Dana-Farber Cancer Institute and Children's Hospital; Harvard Medical School; Boston Massachusetts