Mature teratoma of the placenta.

A rare case of a mature teratoma of the placenta is reported. The tumor lay between the amnion and the chorion and contained skin and its appendages, bone, cartilage, fat and ganglia, without organization. There was no evidence of a recognizable umbilical cord. We concluded that the tumor was a mature teratoma of the placenta. The distinction between a teratoma and a fetus acardius amorphus, and the possible origin of the tumor in this site, are discussed with a brief review of the literature.