Clinicopathologic differences between diploid and tetraploid complete hydatidiform moles

Complete hydatiform moles (CHM) may be are diploid or tetraploid. The proportions vary in the literature. To date, there has not been a systematic characterization of these two types. This study is a retrospective investigation of clinicopathologic differences between diploid and tetraploid CHMs. Thirteen formalin-fixed, paraffin-embedded CHMs were analyzed for DNA content by flow cytometry (FC). Using standard flow cytometric definitions, histograms were classified as FC-diploid or FC-tetraploid (4N peak greater than or equal to 15% of 2N peak and cell cycle events to 8N) and compared with respect to selected clinical and pathologic features. Eight CHMs (61%) met the criteria of tetraploidy by flow cytometry, although all five FC-diploid cases harbored minor (<15%) tetraploid subpopulations. Patients with tetraploid moles were older (mean age 32.8 years vs. 19.6 years, p < 0.005), presented at lower preevacuation gestational ages (12.7 weeks vs. 15.4 weeks, p < 0.05), had higher mean serum beta-HCG levels (2.82 x 10(5) i.u. vs. 0.99 x 10(5) i.u., p = 0.07), and higher DNA S-phase fractions (17.9% vs. 7.0%, p = 0.002). No significant differences were found in other histological features. No moles recurred. In this small sample of CHMs, tetraploidy was common. Compared with the FC-diploid CHMs, FC-tetraploid CHMs occurred in older patients with lower gestational age, higher serum beta-HCG levels, and higher DNA S-phase fraction by flow cytometry.