1. Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Solna, Sweden
2. Department Breast Surgery, Copenhagen University Hospital (Herlev/Gentofte), Copenhagen, Denmark
3. Regional Cancer Centre Uppsala Örebro, Uppsala, Sweden
4. Danish Cancer Society, Cancer Surveillance and Pharmacoepidemiology, Copenhagen, Denmark
5. Cancer Registry of Norway, Oslo, Norway
6. Finnish Cancer Registry, Helsinki, Finland
7. Department of Pathology, University of Helsinki, and HUS Diagnostic Center, Helsinki University Hospital, Helsinki, Finland
8. Swedish Cancer Registry, National Board of Health and Welfare, Stockholm, Sweden
9. Icelandic Cancer Registry, Reykjavík, Iceland
10. Biostatistics Research Group, Department of Health Sciences, University of Leicester, Leicester, UK