1. Department of General and Gastrointestinal Surgery, Mitsui Memorial Hospital, 1 Kanda Izumicho, Chiyoda-Ku, Tokyo 101-8643, Japan
2. Department of Gastroenterology, Mitsui Memorial Hospital, 1 Kanda Izumicho, Chiyoda-ku, Tokyo 101-8643, Japan
3. Department of Pathology, Mitsui Memorial Hospital, 1 Kanda Izumicho, Chiyoda-ku, Tokyo 101-8643, Japan