Malignant change in a mediastinal dermoid cyst

Mature benign cystic teratomas, or dermoid cysts, usually arise in the ovary. They can, however, occur at other sites, including the mediastinum. Malignant change within dermoid cysts is a rare but recognized complication, occurring in 1%-2% of cases. A case of malignant change within a mediastinal dermoid cyst occurring 19 years after initial presentation is described.