1. Department of Pediatrics, Hematology & Oncology, Medical University of Gdansk, Poland
2. Department of Pediatrics, Oncology, Hematology & Diabetology, Medical University of Lodz, Poland
3. Department of Pathology & Neuropathology, Medical University of Gdansk, Poland
4. The English Division Pediatric Oncology Scientific Circle, Medical University of Gdansk, Poland