1. Department of General Surgery, The 306th Hospital of PLA-Peking University Teaching Hospital, Beijing 100101, China
2. Department of General Surgery, Strategic Support Force Medical Center, Beijing 100101, China
3. Department of Pathology, Strategic Support Force Medical Center, Beijing 100101, China
4. Department of Gastroenterology and Hepatology, The First Medical Center, Chinese PLA General Hospital, Beijing 100853, China