1. Department of Endocrinology and Metabolism, Tsukuba University Hospital Mito Clinical Education and Training Center, Mito Kyodo General Hospital, Ibaraki 310-0015, Japan
2. Department of Gastrointestinal Surgery, Tsukuba University Hospital Mito Clinical Education and Training Center, Mito Kyodo General Hospital, Ibaraki 310-0015, Japan
3. Department of Pathology, Tsukuba University Hospital Mito Clinical Education and Training Center, Mito Kyodo General Hospital, Ibaraki 310-0015, Japan