1 Department of Thoracic Surgery and Thoracic Endoscopy, Ruhrlandklinik, West German Lung Center, University Hospital, University of Duisburg-Essen, Essen, Germany.
2 Institute of Pathology, West German Cancer Center, University Hospital Essen, University Duisburg-Essen, Germany.
3 Department of Pediatric Pulmonology, University Children's Hospital Essen, Essen, Germany.