1. Department of General Surgery, Second Affiliated Hospital of Dalian Medical University, Dalian 116044, PR China
2. Department of Pathology and Forensic Medicine, Dalian Medical University, Dalian 116044, PR China
3. Department of Histology and Embryology, Dalian Medical University, Dalian 116044, PR China
4. Department of Pathology, Shanghai Medical College, Fudan University, Shanghai 200032, PR China.