1. Department of Endoscopy, Cancer Institute and Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, P.R. China
2. Department of Gastroenterology and Hepatology, Academic Medical Centre, Amsterdam, The Netherlands
3. Department of Pathology, Cancer Institute and Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, P.R. China
4. Division of Gastroenterology and Hepatology, Mayo Clinic, Scottsdale, Arizona, United States
5. Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland, United States