Voluminous chorionic cyst of the umbilical cord insertion site: a case report

Background. Large subchorionic cysts are extremely rare, and although they rarely have a significant impact on a pregnancy, when located near the umbilical cord insertion, the risk of umbilical cord constriction is increased. This may cause fetal growth retardation and intrauterine asphyxia.
Case presentation. We present a case of an ultrasound-assessed placental subchorionic cyst in a 29-year-old, 0 para, tertigravid woman. The avascular cyst was first found at a gestational age of 22 weeks and measured 31 × 31 mm. After several longitudinal controls, at 39 weeks of pregnancy, the woman delivered a healthy female baby by cesarean section during which the cyst became haemorrhagic. A histopathological examination revealed an amniotic cyst 7 cm in diameter located at the point of insertion of the umbilical cord, which was normovascularised and structured, 20cm in length and whose central insertion appeared velamentous, in the context of a placenta measuring 18 × 16 × 3 cm. The chorionic cyst appeared to be lined with extravillous trophoblast cells, free from atypia.
Conclusions. Serial ultrasound examinations are indicated to assess the risk of altered fetal growth and potential umbilical cord involvement and are therefore essential for planning the appropriate time of delivery.