Résumé
Up to a quarter of ovarian masses originate from germ cells. Germ cell tumours occur at a higher frequency than epithelial tumours in Oriental and African populations. Mature cystic teratomas (MCTs), or the so-called dermoid cysts because of the overall predominance of skin elements, are not only the most common germ cell tumours but also the most common benign ovarian neoplasms in women under 45 years old. This chapter will cover CT and MR appearance of the more common teratomas: mature cystic teratomas; immature teratomas and struma ovarii.