1. Department of Otolaryngology‑Head and Neck Surgery, Hokuto Hospital, Obihiro, Hokkaido 080‑0833, Japan
2. Department of Radiation Therapy, Hokuto Hospital, Obihiro, Hokkaido 080‑0833, Japan
3. Department of Pathology and Genetics, Hokuto Hospital, Obihiro, Hokkaido 080‑0833, Japan
4. Keio Cancer Center, Keio University School of Medicine, Tokyo 160‑8582, Japan
5. Department of Pathology and Translational Pathobiology, Louisiana State University Health Sciences Center at Shreveport, Shreveport, LA 71103, USA