1. Department of endoscopy, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
2. Department of Early diagnosis and treatment of cancer, Feicheng Peoples Hospital, Shandong, China
3. Department of Early diagnosis and treatment of cancer, Yanting Cancer Hospital, Sichuan, China
4. Department of Gastroenterology, Changzhi Peoples Hospital, Shanxi, China
5. Department of Early diagnosis and treatment of cancer, Dongping Peoples Hospital, Shandong, China
6. Department of pathology, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
7. Department of Endoscopy, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, 17 Panjiayuan, Chaoyang District, Beijing 100021, P.R. China