1. Department of Gastroenterology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
2. Division of Molecular Genetic Epidemiology, German Cancer Research Center, Heidelberg, Germany
3. Department of Dermatology, Instituto Valenciano de Oncologia, Valencia, Spain
4. Department of Dermatology, University Hospital Essen, Essen, Germany
5. Center for Primary Health Care Research, Lund University, Malmö, Sweden
6. German Cancer Consortium (DKTK), Essen, Germany