Placental Masses and Pseudomasses

• Chorioangioma: Most common tumor of the placenta. May be a true neoplasm or hamartoma. No metastatic potential. Rare cause of elevated maternal α-fetoprotein. Usually incidental, but large (> 5 cm) or multiple chorioangiomas have high association (up to 50%) with maternal and fetal complications, including polyhydramnios, preterm labor, fetal hemolytic anemia, fetal thrombocytopenia, cardiomegaly, intrauterine growth restriction, toxemia, placental abruption, preeclampsia, and congenital abnormalities. Circumscribed mass with variable echogenicity and anechoic vascular channels. Classically protrudes into the amniotic cavity from the placental surface near the cord insertion.
• Hydatidiform mole: Heterogeneous mass with multiple cystic structures. Color Doppler will show flow between the cysts, but not within the cysts.
• Placental teratoma: Very rare. Look for calcifications to suggest diagnosis.
• Metastases:
• Placental abruption: Retroplacental abruption can mimic a mass. Color Doppler will not show flow in the hematoma.
• Leiomyoma: Leiomyoma under a placenta can mimic a placental mass, especially when hemorrhagic or degenerated. Color Doppler may show uterine vessels splayed around the mass.
• Focal myometrial contraction: Isoechoic to uterine wall. May take up to 30 minutes to resolve and may require follow-up examinations.

References

• Kirkpatrick AD, Podberesky DJ, Gray AE, McDermott JH. Best cases from the AFIP: Placental chorioangioma. Radiographics. 2007 Jul-Aug;27(4):1187-90.
• STATdx.