1. Department of Breast Surgery, The Second Affiliated Hospital of Shandong First Medical University, Tai'an, Shandong 271000, P.R. China
2. The Second Department of General Surgery, Shanxian Central Hospital, He'ze, Shandong 274300
3. Department of Gastrointestinal Surgery, Capital Medical University Affiliated Beijing Shijitan Hospital, Beijing 100038, P.R. China