1. Department of Colorectal and Anal Surgery, Shandong Provincial Qianfoshan Hospital, Shandong University, Jinan, Shandong 250012, P.R. China
2. Department of Hepatobiliary Surgery, Qilu Hospital of Shandong University, Jinan, Shandong 250012, P.R. China
3. Department of Colorectal and Anal Surgery, the First Affiliated Hospital of Shandong First Medical University, Jinan, Shandong 250012, P.R. China
4. Department of Pathology, Jinan Central Hospital Affiliated to Shandong University, Jinan, Shandong 250012, P.R. China
5. Department of Gastrointestinal Surgery, the Second Affiliated Hospital of Shandong First Medical University, Tai'an, Shandong 271600, P.R. China