1. Department of Oncology-Pathology, Karolinska Institutet, Bioclinicum J6:20, Karolinska University Hospital, 171 64 Stockholm, Sweden
2. Department of Otorhinolaryngology—Head and Neck Surgery and Audiology, Copenhagen University Hospital, Rigshospitalet, 2100 Copenhagen, Denmark
3. Department of Clinical Pathology, CCK R8:02, Karolinska University Hospital, 171 64 Stockholm, Sweden
4. Department of Oral Pathology and Radiology, Faculty of Medicine, University of Turku, FI-20014 Turku, Finland
5. Department of Pathology, University of Turku, Turku University Hospital, FI-20014 Turku, Finland