Application of flow cytometry in diagnosis of hydatidiform moles.

We analyzed the nuclear DNA content of 219 hydropic placentas and 68 control (nonhydropic) placentas by flow cytometry (FCM) using formalin-fixed paraffin-embedded tissues. Of 129 cases originally diagnosed as complete hydatidiform mole (CM), 91 were diploid, 25 tetraploid, one triploid, and 12 aneuploid. Of five invasive CM, two were diploid, and three (including one metastasizing mole) were tetraploid. Of 49 partial hydatidiform moles (PM), 36 were triploid and 13 were diploid. Of 41 hydropic abortuses (HA), 34 were diploid, one tetraploid, four triploid, and two aneuploid. Three control placentas were triploid, and the remaining 65 placentas were diploid. Based on FCM and review of the histology, 10 PM were reclassified as HA, and one PM was revised as CM. Four HA were reclassified as PM. One CM was revised as PM. These results show that the difficulty of histologic diagnosis of gestational trophoblastic diseases may lie in PM. Clinical follow-up information was available in 51 CM and 20 PM, and persistent trophoblastic disease followed 18% of CM and 0% of PM. Among diploid complete moles, DNA ploidy did not associate with persistent disease. A significant increase S-phase fraction (SPF) was detected in diploid CM when compared with HA and control placentas. However, among diploid CM, there was no significant difference of SPF between those with and without persistent disease. These findings suggest that DNA measurements by FCM may be an important aid in the diagnosis of hydropic placentas, but not a useful tool for predicting persistent disease.