A rare case of squamous cell carcinoma arising in mature cystic teratoma.

Mature cystic teratoma (MCT) is the most common ovarian tumor. Secondary malignant tumors rarely arise in MCTs, and squamous cell carcinoma (SCC) is the most common form of such tumors. MCT-derived SCC (CIS) is mostly found together with invasive SCC; it is seldom detected alone.