1. Department of Medical Genetics, University of Helsinki, SF-00014 Helsinki, Finland.
2. Department of Medical Sciences, University of Helsinki, and Finnish Red Cross Blood Transfusion Service, SF-00310 Helsinki, Finland.
3. Department of Surgery, Jyväskylä Central Hospital, SF-40620 Jyvaskyla, Finland.
4. Second Department of Surgery, Helsinki University Central Hospital, SF-00290 Helsinki, Finland.
5. Faculty of Medicine, Memorial University of Newfoundland, St. John's, Newfoundland, Canada A1 B 3V6.
6. Department of Pathology, University of Auckland School of Medicine, Auckland, New Zealand.
7. Marshfield Medical Research Foundation, Marshfield, Wl 54449.
8. Departments of Oncology, Pathology, and Epidemiology, Johns Hopkins University School of Medicine and School of Public Health and Hygiene, and Johns Hopkins Hospital, Baltimore, MD 21231.