Clinical difficulties and forensic diagnosis: histopathological pitfalls of villus mesenchymal dysplasia in the third trimester causing foetal death

In this article, the authors present a case of intrauterine foetal death (IUFD). The post-mortem histologic examination revealed placental mesenchymal dysplasia (PMD), a rare human placental disorder. Moreover, cases of PMD are often misdiagnosed as partial mole. The mother was a 26-year-old Italian, whose pregnancy, her first, had been uneventful until week 34⁺⁴ of gestation when IUFD suddenly occurred. The 2350 g male foetus showed no external abnormalities and the karyotype was 46, XY. The placenta weighed 450 g, the chorionic disk was round shaped, measuring 19.5-20.5 cm in diameter and had many enlarged villous structures. Histologically, the parenchyma showed abnormally enlarged and focally hydropic stem villi. Many of them were also surrounded by a fibrinoid material. Neither abnormal trophoblastic proliferation nor inclusion was observed in the examined sections. Causes and pathogenesis of PMD are still unclear and it is difficult to make a diagnosis solely on prenatal ultrasound during pregnancy. Generally, the correct diagnosis is reached only after the histological analysis of the placenta. However, obstetricians and gynaecologists should consider PMD also when a normal looking foetus is accompanied by a molar placenta (index factor for placentomegaly). The authors stress the importance of cooperation and information exchange among clinical and forensic pathologists, neonatologists, obstetricians and gynaecologists to avoid medical malpractice court proceedings in cases of IUFD.