title: Ovarian mature cystic teratoma with fistula formation into the rectum: a case report.
abstract: BACKGROUND
  While ovarian mature cystic teratomas are benign ovarian germ-cell tumors and the most common type of all ovarian tumors, the formation of fistulas into surrounding organs such as the bladder and the intestinal tract is extremely rare. This report documents a case of ovarian mature cystic teratoma with a rectal fistula, thought to be caused by local inflammation.
  
  
  METHODS
  A pelvic mass was diagnosed as an ovarian mature cystic teratoma of approximately 10 cm in diameter on transvaginal ultrasound and magnetic resonance examinations. Endoscopic examination of the lower gastrointestinal tract to investigate diarrhea revealed an ulcerative lesion with hair in the rectal wall adjacent to the ovarian cyst, and formation of a fistula from the ovarian teratoma into the rectum was suspected. Laparotomy revealed extensive inflammatory adhesions between a left ovarian tumor and the rectum. Left salpingo-oophorectomy and upper anterior resection of the rectum were performed. The final pathological diagnosis was ovarian mature cystic teratoma with no malignant findings, together with severe rectal inflammation and fistula formation with no structural disorders such as diverticulitis of the colon or malignant signs.
  
  
  CONCLUSIONS
  The formation of fistulas and invasion into the neighboring organs are extremely rare complications for ovarian mature cystic teratomas. The invasion of malignant cells into neighboring organs due to malignant transformation of the tumor is reported as the cause of fistula formation into the neighboring organs. A review of 17 cases including the present case revealed that fistula formation due to malignant transformation comprised only 4 cases (23.5 %), with inflammation as the actual cause in the majority of cases (13 cases, 76.5 %).
  
  
  CONCLUSIONS
  Although malignancy is the first consideration when fistula formation is observed between ovarian tumors and surrounding organs, in mature cystic teratoma, local inflammation is more likely than malignant transformation.
authors.affiliation: Department of Obstetrics and Gynecology, Saitama Medical Center, Saitama Medical University, 1981 Kamoda, Kawagoe-shi, Saitama Japan.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Kizaki
authors.affiliation: Department of Obstetrics and Gynecology, Saitama Medical Center, Saitama Medical University, 1981 Kamoda, Kawagoe-shi, Saitama Japan.
authors.forename: Tomonori
authors.identifier: 0000-0002-2901-4735
authors.initials: T
authors.lastname: Nagai
authors.affiliation: Department of Obstetrics and Gynecology, Saitama Medical Center, Saitama Medical University, 1981 Kamoda, Kawagoe-shi, Saitama Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Ohara
authors.affiliation: Department of Obstetrics and Gynecology, Saitama Medical Center, Saitama Medical University, 1981 Kamoda, Kawagoe-shi, Saitama Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Gomi
authors.affiliation: Department of Obstetrics and Gynecology, Saitama Medical Center, Saitama Medical University, 1981 Kamoda, Kawagoe-shi, Saitama Japan.
authors.forename: Taichi
authors.initials: T
authors.lastname: Akahori
authors.affiliation: Department of Obstetrics and Gynecology, Saitama Medical Center, Saitama Medical University, 1981 Kamoda, Kawagoe-shi, Saitama Japan.
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Ono
authors.affiliation: Department of Obstetrics and Gynecology, Saitama Medical Center, Saitama Medical University, 1981 Kamoda, Kawagoe-shi, Saitama Japan.
authors.forename: Shigetaka
authors.initials: S
authors.lastname: Matsunaga
authors.affiliation: Department of Obstetrics and Gynecology, Saitama Medical Center, Saitama Medical University, 1981 Kamoda, Kawagoe-shi, Saitama Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Takai
authors.affiliation: Department of Obstetrics and Gynecology, Saitama Medical Center, Saitama Medical University, 1981 Kamoda, Kawagoe-shi, Saitama Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Saito
authors.affiliation: Department of Obstetrics and Gynecology, Saitama Medical Center, Saitama Medical University, 1981 Kamoda, Kawagoe-shi, Saitama Japan.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Baba
authors.affiliation: Department of Obstetrics and Gynecology, Saitama Medical Center, Saitama Medical University, 1981 Kamoda, Kawagoe-shi, Saitama Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Seki
keywords: Diarrhea; Fistula; Inflammation; Ovarian neoplasms; Teratoma