1. Department of Gastroenterology and Hepatology, Landspitali University Hospital, Reykjavik, Iceland;
2. Department of Pathology, Landspitali University Hospital, Reykjavik, Iceland;
3. Faculty of Medicine, University of Iceland, Reykjavik, Iceland;
4. Icelandic Cancer Registry, Icelandic Cancer Society, Reykjavik, Iceland;
5. Department of Surgery, Landspitali University Hospital, Reykjavik, Iceland