*University Clinic for Dermatology, Johannes Wesling Medical Centre, Minden, Germany;

†University Hospital of Ruhr-University, Bochum, Germany;

‡Department of Dermatology, Venereology and Allergology, University Medical Center Göttingen, Göttingen, Germany; and

§Kempf und Pfaltz Histologische Diagnostik, Zurich, Switzerland.

Correspondence: Rudolf Stadler, MD, PhD, University Hospital Johannes Wesling, University of Bochum, Minden, Germany (e-mail: [email protected])

C. Cieslak: Concept, design, definition of intellectual content, literature search, experimental studies, data acquisition, data analysis, statistical analysis, manuscript preparation, manuscript editing, manuscript review, and guarantor; C. Mitteldorf: Concept, design, definition of intellectual content, literature search, data acquisition, data analysis, manuscript editing, manuscript review, and guarantor; T. Krömer-Olbrisch: Data acquisition, data analysis, manuscript editing, and guarantor; W. Kempf: Manuscript editing and guarantor; R. Stadler: Concept, design, definition of intellectual content, literature search, data acquisition, data analysis, manuscript preparation, manuscript editing, manuscript review, and guarantor.

The authors declare no conflicts of interest.

Ethics statement: This study is a retrospective study with annonymized histology slides.

This research received no specific grand from any funding agency in the public, commercial, or no-profit sectors.