1. Department of Otorhinolaryngology, Head and Neck Surgery, Keio University School of Medicine, Tokyo, Japan
2. Department of Otorhinolaryngology, Sano Kosei General Hospital, Sano-shi, Japan
3. Department of Otorhinolaryngology, Saiseikai Yokohamashi Tobu Hospital, Yokohama-shi, Japan
4. Department of Pathology, Keio University School of Medicine, Tokyo, Japan