Prenatal sonographic features of fetal mediastinal teratoma.

Mediastinal teratoma can cause severe hydrops fetalis, which worsens the effects of the mass compression on the vital mediastinal organs. A careful sonographic examination is mandatory to demonstrate the characteristic features suggestive of this congenital tumor. We describe these features at 20 weeks gestation. The most prominent finding was the heterogeneous echogenicity of a large cystic-solid mass with hyperechoic dots, seen as a part of the anterior mediastinum immediately posterior to the sternum. Additional diagnostic features included posterior displacement of the heart, low cardiac output, and hypoplasia of the normally structured heart and lungs due to the direct mass compression. These sonographic findings were confirmed at autopsy which confirmed a nonmetastatic immature teratoma. Sonography may enable accurate diagnosis of mediastinal teratoma considering the anterior location and heterogeneous appearance of the mass, posterior displacement of the heart, normal lung morphology, and compression effects on these organs.