40 year old woman had vaginal bleeding 9 weeks after her last menstrual period (LMP). Her G.P. diagnosed spontaneous miscarriage. Serum human chorionic gonadotropin (HCG) was excessively high.
The enlarged uterus shows the endometrial cavity distended with a profuse proliferation of grape-like, fluid-filled vesicles of variable size (these represent large expanded chorionic villi). The uterine wall is not invaded. No foetus is identifiable.