1. Study Group for Inguinal Lymph Node Metastasis from Colorectal Cancer by the Japanese Society for Cancer of the Colon and Rectum Tokyo Japan
2. Department of Surgery Fujita Health University School of Medicine Toyoake Japan
3. International Medical Center Fujita Health University Hospital Toyoake Japan
4. Department of Gastrointestinal Surgery Tokyo Medical and Dental University Tokyo Japan
5. Division of Colon and Rectal Surgery Shizuoka Cancer Center Sunto‐gun Japan
6. Department of Colorectal Surgery National Cancer Center Hospital Tokyo Japan
7. Department of Surgery Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital Tokyo Japan
8. Department of Surgery Tokyo Metropolitan Health and Hospitals Corporation Ohkubo Hospital Tokyo Japan
9. Department of Surgical Oncology, Faculty of Medicine University of Tokyo Tokyo Japan
10. Department of Gastroenterological Surgery Niigata Cancer Center Hospital Niigata Japan
11. Department of Gastroenterological Surgery Cancer Institute Hospital of the Japanese Foundation for Cancer Research Tokyo Japan
12. Department of Colon and Rectal Surgery University of Texas MD Anderson Cancer Center Houston Texas USA
13. Department of Surgery Kurume University School of Medicine Kurume Japan
14. Department of Gastroenterological Surgery Yamagata Prefectural Central Hospital Yamagata Japan
15. Department of Colorectal Surgery Saitama Medical University International Medical Center Saitama Japan
16. Division of Colorectal Surgery, Department of Surgery Tokyo Women's Medical University Tokyo Japan
17. Department of Surgery Tochigi Cancer Center Tochigi Japan
18. Department of Gastroenterological Surgery Aichi Cancer Center Hospital Nagoya Japan
19. Department of Gastroenterological Surgery Osaka International Cancer Institute Osaka Japan
20. Division of Reparative Medicine, Department of Gastrointestinal and Pediatric Surgery Institute of Life Sciences, Mie University Graduate School of Medicine Tsu Japan
21. Department of Gastrointestinal Hepato‐Biliary‐Pancreatic Surgery Nippon Medical School Tokyo Japan
22. Department of Surgery Matsuyama Red Cross Hospital Matsuyama Japan
23. Division of Medical Safety Section Shiga University of Medical Science Otsu Japan
24. Department of Coloproctological Surgery Juntendo University Faculty of Medicine Tokyo Japan
25. Division of Surgical Oncology, Department of Surgery Nagoya University Graduate School of Medicine Nagoya Japan
26. Department of Medical Statistics Fujita Health University School of Medicine Toyoake Japan