Clinical Challenges

August 2018 - What's your diagnosis?

A 37-year-old woman with no significant past medical history presented with an 8-month history of hemoserous anal discharge. A rectal mass was palpable on digital rectal examination.
Colonoscopy revealed an upper rectal tumor approximately 9 cm from the anal verge that seemed to contain hair (Figure A). Multiple biopsies from this tumor were inconclusive and tumor markers alpha-fetoprotein, carcinoembryonic antigen, and CA 19-9 were unremarkable.
Subsequently, a computed tomography scan of the abdomen and pelvis revealed a left pelvic mass with anterior rectal wall infiltration (Figure B, C).


Mature cystic teratoma of the ovary invading the rectum

The patient was diagnosed with an ovarian dermoid cyst that was fistulating into the rectum. In view of these findings, a decision was made for surgical intervention to remove this lesion. A diagnostic laparoscopy, robotic-assisted left ­salpingo-oopherectomy, excision of cystorectal fistula, proctotomy, and primary repair of the rectal defect was performed. Intraoperative findings include a large left ovarian dermoid cyst with sebaceous content and hair fistulating into the upper rectum just above the rectovaginal pouch, and was adherent to surrounding structures. After excision of the fistula, the anterior rectal wall defect measured 1.5 cm and was closed primarily. Histology revealed a mature cystic teratoma and a fistula tract in the rectum; no malignant features were found. The patient had an uneventful recovery and was well at follow-up.

Mature cystic teratomas of the ovary, also referred to as ovarian dermoid cysts, are benign germ cell tumors of the ovary. These account for 10%-20% of all ovarian neoplasms.1 These are commonly asymptomatic and are found incidentally on imaging studies performed for other indications.2 Complications of these tumors include torsion (16%), rupture (0.5%), and malignant degeneration (2%-6%).3 Rectal invasion via fistulation by these lesions are rare; to date, six cases of colorectal involvement by mature cystic teratomas of the ovary are reported in the literature. These fistulas are a result of rupture of the cyst into the pouch of Douglas, which leads to an intense inflammatory response that results in fistulation, rather than freely into the peritoneum.3 These are therefore undetected until symptoms such as diarrhea or passage of cystic contents (mucus, hair, teeth) develop. The management of mature cystic teratomas of the ovary with symptoms or complications commonly involves surgical intervention to resect the involved ovary and address other pathology.


1. Rajaganeshan R., Wang H., Abouleid A., et al. Conservative surgery in the management of a benign ovarian cystic teratoma presenting as a rectal mass: a case report. Ann R Coll Surg Engl. 2001;93 e46-8.

2. Wichremasinghe D., Samarasekera D. A benign teratoma of the ovary fistulating into the rectum. Ceylon Med J. 2010;55:133.

3. Stern J.L., Buscema J., Rosenshein N.B., et al. Spontaneous rupture of benign cystic teratomas. Obstet Gynecol. 1981;57:363-6.

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