Malignant transformation of an ovarian mature cystic teratoma presenting as a rectal mass

BACKGROUND: Squamous cell carcinoma arising from malignant degeneration of a mature cystic teratoma is rare with a reported incidence of approximately 1-3%. The most common presenting symptoms are lower abdominal pain and increasing abdominal girth of several months' duration. Approximately 50% of the patients present with FIGO stage I while 35-38% present with stage III diseases. CASE: The case described herein represents an unusual presentation and initial diagnostic dilemma of locally aggressive squamous cell carcinoma arising in an ovarian dermoid cyst, with invasion into the distal rectum and anal canal causing rectal bleeding similar to the presentation of anal squamous cell carcinoma. Despite aggressive surgical management with posterior exenteration and optimal tumor debulking followed by 5040-cGy pelvic radiation utilizing 25-MV photons, the patient developed pelvic recurrence at the vaginal cuff 6 weeks after completion of her adjuvant radiotherapy. She subsequently failed cis-platinum single-agent chemotherapy and died 9 months after her initial surgery and diagnosis. CONCLUSION: Squamous cell carcinoma in the anal canal, diagnosed by colonoscopy or proctoscopy, could be an unusual presentation of that arising from malignant degeneration of an ovarian dermoid cyst. This tumor may behave in a locally aggressive manner and be resistant to pelvic radiation or single-agent chemotherapy of cis-platinum. The current experience of adjuvant treatment after comprehensive staging and cytoreductive surgery reported in the world literature is limited, and the optimal management of the malignancy remains unclear.