Molecular and histological characteristics of early triploid and partial molar pregnancies

Molar pregnancy has the highest incidence of all gestational trophoblastic diseases. This is a heterogeneous group of diseases, composed of precancerous lesions and gestational trophoblastic tumours. The hydatidiform mole is characterised by varying degrees of proliferation of syncytiotrophoblastic and cytotrophoblastic cells and stromal oedema. Based on established morphological and cytogenetic criteria, molar pregnancy is divided into partial and complete. The risk of persistent trophoblastic disease is higher in complete moles compared with partial moles. The aim of this study was to assess the importance of additional molecular methods as a conjunction to the standard histopathological analysis to accurately determine the type and origin of triploidy and to detect partial molar pregnancy. This study examined a total of 24 cases of triploidy. Apart from the detailed histomorphological analysis, a molecular analysis of the placental tissue and maternal DNA was also performed. Digynic triploidy was found in 15 cases, whereas diandric triploidy was found in nine of the cases. The results showed that due to the histomorphological overlap between partial molar pregnancy and hydropic abortions, concomitant histopathological analysis of the placental tissue and molecular analysis of the placental and maternal DNA can lead to correct diagnosis.