1. Department of Obstetrics and Gynecology, Shimane University School of Medicine, Izumo, Shimane 6938501, Japan
2. Department of Obstetrics and Gynecology, Seirei Hamamatsu General Hospital, Hamamatsu, Shizuoka 4308558, Japan
3. Department of Pathology, Seirei Hamamatsu General Hospital, Hamamatsu, Shizuoka 4308558, Japan
4. Department of Organ Pathology, Shimane University School of Medicine, Izumo, Shimane 6938501, Japan