1. Department of Otolaryngology; Himeji Red Cross Hospital; Hyogo Japan
2. Department of Otolaryngology Head and Neck Surgery; Himeji Red Cross Hospital; Hyogo Japan
3. Department of Otolaryngology; Okayama Medical Center; Okayama Japan
4. Department of Otolaryngology; Kagawa Rosai Hospital; Kagawa Japan
5. Department of Otolaryngology; Okayama Saiseikai General Hospital; Okayama Japan
6. Department of Pathology; Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences; Okayama Japan