1. Department of Gastroenterology and Hepatology, Amsterdam UMC location University of Amsterdam, Amsterdam, the Netherlands
2. Cancer Center Amsterdam, Amsterdam, the Netherlands
3. Amsterdam Gastroenterology Endocrinology Metabolism, Amsterdam, the Netherlands
4. Gastrounit, Copenhagen University Hospital - Amager and Hvidovre, Danish Polyposis Registry, Hvidovre, Denmark
5. Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
6. Department of Gastrointestinal Oncology, Netherlands Cancer Institute, Amsterdam, the Netherlands
7. Department of Gastroenterology and Hepatology, Leiden University Medical Center, Leiden, the Netherlands
8. Department of Gastroenterology, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), University of Barcelona, Hospital Clínic de Barcelona, Barcelona, Spain
9. Department of Oncological Gastroenterology and Department of Cancer Prevention, Maria Sklodowska-Curie National Research Institute of Oncology, Warsaw, Poland
10. Department of Surgery, Amsterdam UMC location University of Amsterdam, Amsterdam, the Netherlands
11. Department of Epidemiology and Data Science, Amsterdam UMC location University of Amsterdam, Amsterdam, the Netherlands
12. Policlinico di Sant'Orsola, IRCCS Azienda Ospedaliero-Universitaria di Bologna, Bologna, Italy
13. Department of Medical and Surgical Sciences, University of Bologna, Bologna, Italy
14. Polyposis Registry, St Mark's Hospital, Harrow, United Kingdom
15. Department of Surgery and Cancer, Imperial College London, London, United Kingdom
16. Instituto de Investigación Biomédica ISABIAL, Universidad Miguel Hernández, Servicio de Medicina Digestiva, Hospital General Universitario de Alicante, Alicante, Spain