Partial Hydatidiform Mole

Abstract: CLASSIC hydatidiform mole is the product of an abnormal pregnancy with grossly swollen chorionic villi, but without an embryo, cord or amniotic membrane. Histologically, the villi are characterised by advanced hyperplasia and anaplasia of the trophoblast, oedema of the stroma and the absence of foetal capillaries1. A malignant change to invasive mole or choriocarcinoma is frequent. The karyotype of the mole is predominantly, if not exclusively, 46,XX. We have made a cytogenetic study of the origin of hydatidiform mole and found that it receives only paternal chromosomes and is therefore androgenetic in origin.

Abstract: One hundred and six triploids were ascertained during a study of 1500 consecutive spontaneous abortions. The mechanism of origin of the additional haploid complement was investigated by comparing parental and foetal cytogenetic heteromorphisms and a histopathological examination of each triploid was done in a subsequent blind study. The mechanism of origin of the additional haploid complement was found to be highly correlated with the development of partial hydatidiform mole and with gestational age. All 51 paternally derived triploids in which a pathologic diagnosis could be made were partial moles, whereas only 3 of 15 maternally derived triploids on which a diagnosis could be made were molar. The mean gestational age of the paternally derived triploids was 122 days while that of the maternally derived triploids was only 74 days. It was suggested that the development of partial mole was primarily associated with the presence of two paternal haploid chromosome complements, the association with relatively long gestational ages being a secondary one consequent upon retention of the molar placentae for many weeks after foetal demise.