Early partial hydatidiform mole: prevalence, histopathology, DNA ploidy, and persistence rate

The widespread use of ultrasound in the diagnosis and management of intrauterine fetal death has resulted in moles being evacuated earlier than before. In order to clarify clinicopathologic features of early partial mole (PM), morphology and DNA ploidy of early (≤12 gestational weeks) and late (>12 gestational weeks) partial PM were studied. A total of 80 early and 20 late PMs (37 from 1981–90; 63 from 1991–98) were analyzed. Mean gestational ages were 9.6 weeks for early PMs and 14.8 weeks for late PMs. Early PM was more common in 1991–1998 (57/63, 90%) than in 1981–1990 (23/37, 62%). Pre-evacuation diagnosis of hydatidiform mole was achieved in only 4 early and 1 late PMs. There were no significant differences in histology between early and late PMs, except that villi were smaller in early PMs and there was extensive stromal fibrosis in late PMs. Ploidy was as follows: 70 of 80 early PMs and 19 of 20 late PMs were triploid, 5 early PMs were aneuploid, and 5 early and 1 late PM were diploid. None of 45 patients with early PM and 1 of 11 with late triploid PM developed persistent gestational trophoblastic disease. Early PM is now more prevalent than it was previously. This may be a result of greater awareness of the entity of PM, its increased recognition by pathologists and the widespread use of ultrasound in the diagnosis and management of intrauterine fetal death. The diagnosis of PM should be based on pathological examination, since most PMs still elude clinical detection. DNA ploidy analysis is useful in the evaluation of problem cases. The risk of persistent disease seems to be very low in the case of early PMs. Received: 6 December 1999 / Accepted: 1 March 2000