Placental mesenchymal dysplasia: a rare clinicopathologic entity confused with molar pregnancy

Placental mesenchymal dysplasia (PMD) is a rare placental abnormality characterised by placentomegaly and grape-like vesicles resembling partial mole by ultrasonography, but in contrast to partial mole can co-exist with a viable fetus. Although the karyotype is normal, the fetus is at increased risk for intrauterine growth restriction, intrauterine fetal demise or perinatal death and Beckwith-Wiedemann syndrome. Prenatal diagnosis is difficult and the final diagnosis is usually achieved by postpartum histological examination of the placenta. We present two recent cases of placental mesenchymal dysplasia with poor obstetric outcome. One fetus presented with reduced growth parameters, while the other fetus showed hepatosplenomegaly and early hydropic changes that appear to be associated with Beckwith-Wiedemann syndrome. In this report, the clinico-pathological features of two cases of PMD are discussed and the differentiation from a partial mole is highlighted. This study also supports the utility of cytogenetic ploidy analysis and p57KIP2 protein staining in the evaluation of pregnancies with PMD.