Trophoblast proliferation rate does not predict progression to persistent gestational trophoblastic disease in complete hydatidiform mole

Persistent gestational trophoblastic disease (PGTD) is a significant complication of complete hydatidiform mole. There are, however, no reliable clinical or pathological parameters to predict the development of PGTD following the evacuation of a complete mole. In this study we examined the value of Ki67 expression in the prediction of PGTD following complete mole. Immunohistochemistry for Ki67 was performed on 21 cases of complete mole complicated by PGTD and 17 cases that resolved spontaneously after evacuation. Strong Ki67 expression was seen in both villous cytotrophoblast and extravillous trophoblast of the complete moles. The Ki67 index of extravillous trophoblast was significantly higher than that of villous cytotrophoblast. There was no significant difference in Ki67 index of either villous cytotrophoblast or extravillous trophoblast between cases of complete mole complicated by PGTD and those that resolved spontaneously. Trophoblast proliferation rate does not predict outcome following complete hydatidiform mole. Other factors involved in myometrial invasion may be of importance in the development of this complication, but serum chorionic gonadotrophin level is the only reliable predictor of the development of persistent gestational trophoblastic disease.