1. Department of General Surgical Science, Gunma University, Graduate School of Medicine, Maebashi, Gunma 371‑8511, Japan
2. Department of Gastroenterological Surgery, Gunma Prefectural Cancer Center, Ohta, Gunma 373‑8550, Japan
3. Department of Gastroenterological Surgery, Saitama Red Cross Hospital, Ohmiya, Saitama 330‑8553, Japan
4. Department of Human Pathology, Juntendo University Graduate School of Medicine, Bunkyouku, Tokyo 113‑8421, Japan