Department of Gastroenterology, Yokohama City University Hospital, Kanagawa, Japan
2.Department of Gastroenterology, Tokyo Metropolitan Hiroo Hospital, Tokyo, Japan
3.Department of Pathology, Tokyo Metropolitan Hiroo Hospital, Tokyo, Japan
4.Department of Medical Education, Yokohama City University School of Medicine, Kanagawa, Japan
5.Department of Gastroenterology, Yokohama City University Hospital, Kanagawa, Japan; Office of Postgraduate Medical Education, Yokohama City University Hospital, Kanagawa, Japan