1. Department of Otorhinolaryngology-Head and Neck Surgery, Chung-Ang University College of Medicine, Seoul, Korea.
2. Department of Otolaryngology-Head and Neck Surgery, Konkuk University College of Medicine, Seoul, Korea.
3. Department of Otorhinolaryngology, Yonsei University College of Medicine, Seoul, Korea.
4. Department of Pathology, Yonsei University College of Medicine, Seoul, Korea.