1. Department of Dermatology, Venerology and Allergology, HELIOS St Elisabeth Hospital Oberhausen, University Witten/Herdecke, Oberhausen, Germany
2. Institute of Pathology, Mülheim an der Ruhr, Mülheim, Germany
3. Institute of Virology, National Reference Center for Papilloma-and Polyomaviruses, University of Cologne, Cologne, Germany