Squamous cell carcinoma and pleomorphic sarcoma (MFH) arising in a mature cystic teratoma of the ovary.

Malignant transformation of a mature ovarian teratoma is a rare occurrence predominantly in the postmenopausal period. All histologic types can be seen; however, squamous cell carcinoma accounts for over 75% of cases. Sarcomatous transformation is much more uncommon, with cases of angiosarcoma, rhabdomyosarcoma, leiomyosarcoma and liposarcoma arising in a mature ovarian teratoma described in literature. We report a case of squamous cell carcinoma and pleomorphic sarcoma arising in a mature cystic teratoma of the ovary in a 58-year-old woman. The tumor shows both epithelial and stromal components. The epithelial component is moderately-differentiated squamous cell carcinoma with foci of keratinization. The stromal component is significant for an abundance of giant cells, enlarged bizarre nuclei, and marked mitotic activity. This is a unique report of malignant transformation of a benign ovarian teratoma showing both epithelial and sarcomatous elements.