Extravillus endovascular implantation site trophoblast invasion is abnormal in complete versus partial molar pregnancies

This study examines endovascular trophoblast invasion in pregnancies compli cated by complete hydatidiform mole (C-NI), partial hydatidiform mole (PM) and non-molar abortions (HA). Two hundred consecutive cases from a supra-re gional referral centre for suspected trophoblastic disease were examined hi stologically with particular regard to the presence or absence of endovascu lar trophoblast invasion of decidual vessels. There were 57 CM, 75 PM and 6 8 HA. The prevalence of normal endovascular invasion of decidual vessels wa s significantly lower in CM compared to all other clinical groups, amongst which there were no significant differences. Endovascular trophoblast was i dentified in about 80 per cent of HA and PM moles, compared to only around 25 per cent of CM (Z = - 4.0, P <0.0001). The majority of cases of complete mole demonstrated a similar appearance, of implantation site showing flori d interstitial extravascular trophoblast invasion with surrounding of decid ual vessels but without normal endovascular trophoblast invasion or 'pluggi ng' seen. In many cases, there also appeared to be destruction of decidual vessels with interstitial haemorrhage and extensive fresh blood clot presen t in the histological sections. These findings may provide some explanation regarding the mechanism of clinical findings in molar pregnancy. (C) 2001 Harcourt Publishers Ltd.