Choriocarcinoma and partial hydatidiform moles

Background Partial hydatidiform moles (PMs) rarely require chemotherapy and have never previously been proven to transform into choriocarcinoma, the m ost malignant form of gestational trophoblastic disease (GTD). Consequently , some have questioned whether women with PMs need human chorionic gonadotr opin (hCG) follow-up. Here, we investigate whether PMs can transform into c horiocarcinomas. Methods Patients with a PM who developed a subsequent choriocarcinoma were identified from our GTD database. The histology of both PM and ensuing chor iocarcinoma was reviewed and flow cytometry used to verify the triploid sta tus of the PMs. To determine whether the choriocarcinoma arose from the PM, DNA from the PM and choriocarcinoma in each patient was compared using mic rosatellite polymorphisms. Findings Of the 3000 patients with PM, 15 required chemotherapy for persist ing GTD. This was identified as choriocarcinoma in three cases. In one pati ent, the local pathologist could not differentiate between a PM or a hydrop ic abortion and neither central histological review nor hCG follow-up were obtained. This patient nearly died before the diagnosis of choriocarcinoma was made. Fortunately, the local pathologists correctly diagnosed PM in the two other patients who were then registered for hCG follow-up. Some months later, the hCG was rising and repeat uterine evacuation revealed choriocar cinoma. The PM was confirmed to be triploid in all three cases and genetic analysis showed that the subsequent choriocarcinomas contained identical si ngle maternal and two paternal alleles at several independent loci. Interpretation Our results show that PMs can transform into choriocarcinoma , All patients with suspected PM should be reviewed centrally and, if confi rmed, need hCG follow-up.