Flow cytometric DNA analyses of 105 fresh hydatidiform moles, with correlations to prognosis.

Cellular DNA contents of consecutive hydatidiform moles were analysed by flow cytometry of unfixed samples, freed of maternal tissue and treated with detergent and trypsin, using two external controls. DNA-diploidy was found in 62 moles, DNA-triploidy in 42 and DNA-tetraploidy in one. Two non-molar placentas and two invasive moles were found to be DNA-diploid. In 28 of 42 DNA-triploid moles, trophoblastic hyperplasia was not noted, making the discrimination between vesicular abortions with or without trophoblastic hyperplasia unwarranted on genetic grounds. A good fit was obtained to a distribution with one G0-1 peak in 49 cases, whereas 60 cases showed two peaks. Technical artifacts, created by flow cytometry, were excluded. Differences in the nuclear accessibility for the dye and degradation of DNA are unlikely causes of this heterogeneity. The existence, in vivo, of two or more cell populations with different DNA contents is a reasonable explanation. The criteria for persistent trophoblastic disease were standardised. Eight cases of persistent trophoblastic disease were observed among the 62 DNA-diploid moles (13%); no case was observed after DNA-triploid or DNA-tetraploid moles. Combining these data, with those of other studies where ploidy was determined using optimal techniques [10,13], allows the calculation of 95%-confidence-limits for the risk of persistent trophoblastic disease after a triploid mole to 0-2.7%.