1. Department of Hepato-Biliary-Pancreatic and Gastrointestinal Surgery, School of Medicine, International University of Health and Welfare, Chiba 286-0124, Japan
2. Departments of Surgery, Keio University School of Medicine, Tokyo 160-8582, Japan
3. Department of Pediatric Surgery and Transplantation, Kumamoto University Graduate School of Medical Sciences, Kumamoto 860-8556, Japan
4. Departments of Pathology, Keio University School of Medicine, Tokyo 160-8582, Japan