1. Department of Paediatrics, Japanese Red Cross Maebashi Hospital, Gunma 371-0811, Japan
2. Department of Pathology, Japanese Red Cross Maebashi Hospital, Gunma 371-0811, Japan
3. Department of Paediatrics, Gunma University, Gunma 371-8511, Japan
4. Division of Leukaemia and Lymphoma, Children’s Cancer Centre, National Centre for Child Health and Development, Tokyo 157-0074, Japan
5. Department of Paediatrics, Jichi Medical University, Tochigi 329-0498, Japan