1. Department of Otolaryngology, Tohoku Kosai Hospital, 2-3-11 Kokubun-cho, Aoba-Ku, Sendai 980-0803, Japan
2. Department of Otolaryngology, Head and Neck Surgery, Tohoku University School of Medicine, 1-1 Seiryo-machi, Aoba-Ku, Sendai 980-8574, Japan
3. Department of Pathology, Tohoku University Hospital, 1-1 Seiryo-machi, Aoba-Ku, Sendai 980-8574, Japan
4. Department of Otolaryngology, Osaki Citizen Hospital, 3-8-1 Furukawahonami, Osaki, Miyagi 989-6136, Japan