Ovarian mature cystic teratoma with fistula formation into the rectum: a case report
© The Author(s) 2016
Received: 24 February 2016
Accepted: 28 September 2016
Published: 3 October 2016
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.
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.
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 %).
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.
Ovarian mature cystic teratomas are benign ovarian germ-cell tumors and the most common type of all ovarian tumors, comprising 10–25 % of cases (Tandon et al. 2010). The most common known complication is torsion of the tumor, reportedly observed in approximately 16 % of cases (Tandon et al. 2010; Park et al. 2008). Meanwhile, formation of fistulas into neighboring organs is an extremely rare complication, occurring in less than 1 % of cases (Tandon et al. 2010; von-Walter 2012) and seldom reported. In the present case, endoscopy of the lower gastrointestinal tract performed to investigate refractory diarrhea resulted in the incidental discovery of a rectal fistula originating from an ovarian mature cystic teratoma.
Ovarian mature cystic teratomas are the most common ovarian tumor, comprising 10–25 % of all cases (Tandon et al. 2010). Multiple complications are known, of which the most common is torsion (16 % of tumors). Other reported complications include rupture (1–4 %), malignant transformation (1–2 %), and infection (1 %) (Park et al. 2008). Meanwhile, the formation of fistulas and invasion into the neighboring organs are extremely rare complications for this tumor, with frequency said to be less than 1 % (Tandon et al. 2010; von-Walter 2012).
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 (Mitui et al. 1983; Okada et al. 2005; Song and Conner 2012; Gooneratne et al. 2015), but malignant transformation is not a necessary condition for the formation of fistulas (Kim et al. 1999).
In this instance, we performed surgery in consideration of the possible presence of a malignant tumor as the cause of fistula formation. Pathological diagnosis performed during surgery identified the tumor as a benign ovarian mature cystic teratoma. Histological examination of the area around the rectal fistula was deemed necessary to rule out the possibility of a malignant tumor, and an upper anterior resection of the rectum was performed. However, no signs of malignancy were found, and it was concluded that the fistula formation was due to inflammation. A retrospective review would suggest that the surgery conducted in this case (upper anterior resection of the rectum) was over-treatment, and trimming and restoration of the fistula site might have been sufficient. However, we believed that malignancy together with the invasion of malignant cells into neighboring organs was a necessary condition for the formation of fistulas.
Reported cases of ovarian teratoma complicated with fistula formation
Author (date of publication)
Cause of fistula formation
Mitui et al. (1983)
Diarrhea containing hair
Sigmoid colon, small intestine
RS, colostomy, PRSI
Shiels et al. (1986)
USO, fistulectomy, repair of the bowel defect
Ulstein et al. (1987)
Landmann et al. (1988)
Suzuki et al. (1999)
Bladder, small intestine
TH, BSO, appendectomy, PRSI, PC
Tabata et al. (2004)
Okada et al. (2005)
Abdominal pain, watery diarrhea
TH, BSO, PRSI, POM
Cebesoy et al. (2009)
Abdominal pain, purulent diarrhea
Tandon et al. (2010)
Rajaganeshan et al. (2011)
Weight loss, loose stools, rectal bleeding
USO, repair of the bowel defect
Salame et al. (2011)
von-Walter et al. (2012)
Small bowel obstruction
Small intestine, transverse colon
USO, PRSI, repair of the bowel defect
Song et al. (2012)
Abdominal pain, constipation
Conway et al. (2012)
Abdominal pain, nausea
Repair of the bowel defect
Gooneratne et al. (2015)
Abdominal distention, bloody diarrhea
Shiels et al. (1986) consider the following steps to be involved in the pathogenesis of fistula formation: (1) rupture or perforation of the cyst, (2) small leakage from the cyst causing dense adhesion between the cyst and the surrounding organs, (3) circulatory disturbance of the walls of these structures due to the resultant necrosis and inflammation, and (4) formation of fistulas in the walls of these structures. In addition, they have mentioned that rupture or perforation of the cyst is likely caused by circulatory disorders or infection due to factors such as partial torsion, malignant transformation, and mechanical forces.
Fistula formation was observed in 20 sites in 17 patients, listed by organ as the urinary bladder (5 cases, 25.0 %), small intestine (5 cases, 25.0 %), sigmoid colon (4 cases, 20.0 %), rectum (4 cases, 20.0 %), and transverse colon (2 cases, 5.0 %). While Kim et al. (1999) have reported that fistulas are most likely to form in the urinary bladder, we consider their formation equally likely in any organ neighboring the tumor, or more likely to form in the lower gastrointestinal tract. Further, the symptoms presented will depend on the organ into which a fistula has formed.
Of the 13 cases in which inflammation was the cause, including the case we experienced, extended surgery appears to have been performed because of the possibility of malignancy in at least 5 cases (38.5 %). We too performed extended surgery in consideration of the possibility of a malignant tumor, but with the knowledge that inflammation is an extremely common cause of fistula formation from ovarian mature cystic teratomas, more limited surgery might have been possible, and we must reflect upon this point.
Formation of fistulas into neighboring organs is an extremely rare complication of ovarian mature cystic teratomas. In the present case, we experienced the fistula formation into the rectum, and concerned about the possibility of malignancy, nevertheless no malignancy was observed. While opportunities to encounter such a case in clinical practice seldom arise, if a case is encountered or this complication is suspected, treating doctors must remember that the presence of malignant transformation is not a necessary condition for formation, and in fact inflammation is the cause in most cases. While surgical intervention is necessary when the formation of fistulas is observed, it should be performed subject to a thorough assessment of the possible causes and with due attention to the avoidance of over-treatment.
YK was a major contributor in writing the manuscript. TN contributed to the study concept and design and was involved in drafting and revising the manuscript. KO, YG, TA and SM participated in the actual treatment of the patient. YO, MS and YT were involved in revising the manuscript. KB carried out the ultrasonographic measurements. HS supervised the study, critiqued the study design, edited and commented on the manuscript. All authors read and approved the final manuscript.
The authors thank all the doctors in our department for their assistance during this study.
The authors declare that they have no competing interests.
Written informed consent was obtained from the patient for the publication of this report and any accompanying images.
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