1. Department of Otolaryngology, Head and Neck Surgery Tohoku University Hospital Sendai Japan
2. Division of Otolaryngology Tohoku Medical and Pharmaceutical University Hospital Sendai Japan
3. Center for Otologic Surgery Sen‐en Rifu Hospital Rifu Miyagi Japan
4. Technical Services Division Tohoku Medical and Pharmaceutical University Sendai Japan
5. Division of Pathology Tohoku Medical and Pharmaceutical University Hospital Sendai Japan
6. Department of Pathology Tohoku University School of Medicine Sendai Japan