1. Surgical Department L, Aarhus University Hospital, Aarhus, Denmark
2. Department of Epidemiology and Social Medicine, University of Aarhus, Aarhus, Denmark
3. Danish Polyposis Register, Department of Surgical Gastroenterology, Hvidovre Hospital, Hvidovre, Denmark
4. Finnish Polyposis Register, Department of Surgery, Helsinki University Central Hospital, Helsinki, Finland
5. Norwegian Polyposis Register, Department of Surgery, Akershus Central Hospital, Nordbyhagen, Norway
6. Swedish Polyposis Register, Department of Gastroenterology and Hepatology, Karolinska Hospital, Stockholm, Sweden
7. Colorectal Unit, Sahlgrenska University Hospital Östra, Gothenburg, Sweden