1. Department of Otorhinolaryngology/Head and Neck Surgery, University Medical Center Groningen, University of Groningen, 9700 RB Groningen, The Netherlands
2. Department of Surgery, St. Antonius Hospital, 3543 AZ Utrecht, The Netherlands
3. Department of Pathology, University Medical Center Groningen, University of Groningen, 9723 GZ Groningen, The Netherlands