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