1. Department of Otolaryngology, Japanese Red Cross Society Himeji Hospital, Himeji, Hyogo, Japan;
2. Department of Otolaryngology Head and Neck Surgery, Kumamoto University Graduate School of Medicine, Kumamoto, Kumamoto, Japan;
3. Department of Otolaryngology Head and Neck Surgery, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Okayama, Japan;
4. Department of Pathology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Okayama, Japan