1. Institute of Cytopathology, Heinrich Heine University, Moorenstr. 5, D‐40225 Düsseldorf, Germany
2. Institute of Pathology, Heinrich Heine University, Moorenstr. 5, D‐40225 Düsseldorf, Germany
3. Division of Cytopathology, Institute of Pathology, University Hospital Basel, Schönbeinstr. 40, CH‐4003 Basel, Switzerland