1. 1 Department of Dermatology, Venereology and Allergology, Dr Georgi Stranski University Hospital, Faculty of Medicine , Medical University – Pleven , Bulgaria
2. 2 Department of General and Clinical Pathology, Faculty of Medicine , Medical University – Pleven , Bulgaria
3. 3 Surgical Oncology Department, Dr Georgi Stranski University Hospital, Faculty of Medicine , Medical University – Pleven , Bulgaria
4. 4 Department of Nuclear Medicine, Radiation Therapy and Medical Oncology, Tsaritsa Yoanna University Hospital, Faculty of Medicine , Medical University – Sofia , Bulgaria