1. Department of Gynecology, Qingdao Women and Children Hospital, Qingdao, Shandong 266000, P.R. China
2. Department of Pathology, Qingdao Municipal Hospital (Group), Qingdao, Shandong 266000, P.R. China
3. Department of Gynecology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong 266000, P.R. China