1. Department of Gastrointestinal Surgery, Tokyo Medical and Dental University, Tokyo, Japan;
2. Department of Head and Neck Surgery, Tokyo Medical and Dental University, Tokyo, Japan;
3. Department of Otorhinolaryngology-Head and Neck Tumor Surgery, Tokyo Toritsu Komagome Byoin, Tokyo, Japan;
4. Department of Human Pathology, Tokyo Medical and Dental University, Tokyo, Japan