Sonographic diagnosis of placental teratoma.

Placental teratomas are very rare, and the features that distinguish them on sonography and allow their differentiation from other placental tumors have not been fully described. Prenatal recognition of this tumor is prognostically useful because, unlike other neoplasms, placental teratoma is benign and almost never associated with congenital deformities in the fetus. We describe the case of a 27-year-old pregnant woman in whom prenatal color Doppler sonographic examination performed during early-stage labor revealed a heterogeneous mass at the placental margin. This lesion, which measured 10 x 8 x 5 cm, had an echogenic focus consistent with calcification and hyperechoic foci consistent with fat. Placental teratoma and fetus acardius amorphus were considered in the differential diagnosis, but the segmental organization and umbilical cord-like structures that characterize the latter diagnosis were absent. The sonographic diagnosis, placental teratoma, was confirmed postnatally by histopathologic examination. The neonate, a healthy boy, was delivered vaginally at term. Although the presence of tissues of varied echogenicity, such as calcification, fat, and fluid, and the absence of both polarity and an umbilical cord-like structure support the sonographic diagnosis of placental teratoma, fetus acardius amorphus should be considered in the differential diagnosis. Histopathologic examination may be needed to establish a definitive diagnosis in such cases.