[Adenosquamous carcinoma arising in a dermoid cyst (benign cystic teratoma) of the ovary--a case report].

An 89-year-old woman with adenosquamous carcinoma arising in a dermoid cyst (benign cystic teratoma) of the ovary is reported. The malignant change of a dermoid cyst is rare. To our knowledge, this is the first report case of an adenosquamous carcinoma arising in a dermoid cyst of the ovary. Moreover, this case is the oldest patient on record. It is important that dermoid cyst be examined carefully.