Multimodality imaging of placental masses: a pictorial review

Placental masses are uncommonly identified at the time of obstetric ultrasound evaluation. Understanding the pathologies presenting as placental masses is key for providing a differential diagnosis and guiding subsequent management, which may include additional imaging with magnetic resonance (MR) imaging. Potential benign entities include chorioangiomas and teratomas. Larger chorioangiomas can cause fetal cardiovascular issues from volume overload. Placental mesenchymal dysplasia has an association with fetal anomalies and detailed fetal evaluation should be performed when it is suspected. Identifying other cystic masses such as partial and complete moles is crucial to prevent erroneous pregnancy termination. This review addresses normal imaging appearance of the placenta on ultrasound and MR imaging and describes various trophoblastic and nontrophoblastic placental masses. Potential placental mass mimics including uterine contractions and thrombo-hematomas are also presented.