Malignant degeneration of mature cystic teratomas.

Malignant transformation of benign cystic teratoma is rare and the most common malignancy is squamous cell carcinoma. The diagnosis is rarely made preoperatively and the prognosis is usually poor. We report 4 cases with dermoid cysts showing malignant transformation, 3 with squamous carcinoma and 1 with adenocarcinoma. The patients were within the reproductive age and underwent surgical intervention with intraoperative evaluation. Frozen section identified 2 cases with malignant transformation and staging laparotomy was performed at the initial laparotomy. One of the remaining underwent reoperation following a pregnancy termination and the other refused further surgery. None had metastases and/or capsule invasion. One had tumour rupture during excision and received combined chemotherapy following surgery. Three of the patients remain well and 1 is lost to follow-up.