Genetic evidence that placental site trophoblastic tumours can originate from a hydatidiform mole or a normal conceptus.

The genetic origin of two placental site trophoblastic tumours was established using a Y chromosome-specific and locus-specific minisatellite probes. A gestational origin was confirmed for both tumours. In one case the origin of the tumour was consistent with derivation from a normal female conceptus while the other was shown to arise from a homozygous complete hydatidiform mole, an abnormal conceptus more usually associated with the development of choriocarcinoma.