1. Department of Visceral, Vascular and Endocrine Surgery, Martin Luther University Halle-Wittenberg , Ernst-Grube-Str. 40 , Halle (Saale) D-06097, Germany
2. Department of Pathology, Martin Luther University Halle-Wittenberg , Halle (Saale) , Germany
3. Division of Endocrine Surgery, Department of General, Visceral and Transplantation Surgery, University of Duisburg-Essen , Essen , Germany