Unusual presentations of fetal teratoma.

Teratomas are the most common congenital neoplasm. Fetal intracranial teratomas generally are large solid/cystic tumors that often completely replace normal brain tissue. Mediastinal teratomas are uncommon and rarely result in nonimmune hydrops fetalis. We describe two unusual presentations of fetal teratoma. The first is a fetus with massive hydrocephalus and marked facial deformities that were caused by a small intracranial teratoma. The second is a fetus with a mediastinal teratoma associated with non-immune hydrops fetalis. In both cases, compression by the mass resulted in lethal sequelae.