Distinctive flow histogram pattern in molar pregnancies with elevated maternal serum human chorionic gonadotropin levels

Background. Flow cytometric analysis of trophoblastic tissue has shown that most partial hydatidiform moles (PMs) are triploid, whereas most complete moles (CMs) are diploid or tetraploid. Ploidy analysis can support a diagnosis of CM or PM. However, in some cases, a precise diagnosis cannot be rendered. Methods. This study examined DNA flow histograms in 86 cases of histologically diagnosed moles and nonmoles to identify patterns specific to moles to eliminate indeterminate diagnoses. Forty hydropic abortions, 17 CMs, and 29 PMs were analyzed, and results were correlated with microscopic appearance and maternal serum human chorionic gonadotropin (HCG) levels. Results. Analysis of nondiploid histologic moles in which the initial maternal serum HCG level was greater than 150,000 mIU/ml showed similar histograms in 12 of 14 cases. In these 12 specimens, a distinct aneuploid peak could not be delineated from multiple cell populations between the G0/G1 and G2/M or G0/G1_diploid and G0/G1_aneuploid peaks. This commonly appeared as a slope rising toward the tetraploid region. S‐phase fraction values showed a trend toward higher values in the moles versus nonmoles, but the difference was not statistically significant. Conclusions. This sloping histogram pattern may reflect progression from a single aneuploid to multiple aneuploid populations. Its statistically significant correlation (P > 0.001) with high maternal serum HCG values suggests the presence of a highly metabolically active population of aneuploid trophoblast. Because it appears specific to nondiploid moles, recognition of the pattern will aid in the distinction of mole from hydropic spontaneous abortion. Cancer 1994; 73:2782–90.