[Rapidly developing benign teratoma of the mediastinum in the adult]

Benign mediastinal teratomas are rare entities, representing 8 to 18% of all mediastinal tumors. Two cases of benign teratomas with a rapid growth suggesting malignancy are reported. CT and MR allowed precise characterization of the multi-tissue composition of the tumor (various CT densities were noted corresponding to adipose, cystic, calcified and hemorrhagic components), and definition of the extension of the process before surgical removal. The per-operative pathological analysis in one patient confirmed the benign nature of the lesion based on the absence of immature tissue, allowing complete surgical removal. The final pathological examination showing mucus secretion by bronchial glandular tissue and intra-tumoral hemorrhage may explain the rapid growth of this kind of lesion. The post-operative follow-up of these benign teratomas is favourable.