1. Department of Pediatrics; Aarhus University Hospital; Aarhus Denmark
2. Danish Cancer Society Research Center; Copenhagen Denmark
3. Department of Clinical Sciences, Pediatric Oncology and Hematology; Skåne University Hospital, Lund University; Lund Sweden
4. The Finnish Cancer Registry; Helsinki Finland
5. The Icelandic Cancer Registry; Reykjavik Iceland
6. Faculty of Medicine; University of Iceland; Reykjavik Iceland
7. Cancer Registry of Norway; Oslo Norway
8. Department of Hepatology and Gastroenterology; Aarhus University Hospital; Denmark