1. Department of Obstetrics and Gynecology, Qilu Hospital of Shandong University, Jinan, Shandong 250012, P.R. China
2. Department of Pathology, School of Medicine, Shandong University, Jinan, Shandong 250012, P.R. China
3. Department of Pathology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9072, USA
4. Department of Diagnostics, School of Medicine, Shandong University, Jinan, Shandong 250012, P.R. China