INCIDENCE OF HYDATIDIFORM MOLE IN A TOKYO HOSPITAL - A 5-YEAR (1989 TO 1993) PROSPECTIVE, MORPHOLOGICAL, AND FLOW CYTOMETRIC STUDY

This prospective study reports the incidence of hydatidiform mole (HM) in a population of 13,510 pregnancies in a Tokyo hospital over a 5-ye ar period between 1989 and 1993. During this period all ''products of conception'' from first- and second-trimester abortions were histologi cally reviewed, and 76 hydropic placentas were retrieved and analyzed by flow cytometry (FCM). Of 23 specimens originally diagnosed as compl ete hydatidiform mole (CM), 21 were dip diploid, and two were aneuploi d (nontriploid/tetraploid). Of 22 partial hydatidiform moles (PMs), 20 were triploid, and two were diploid. Of 31 hydropic abortions (HAs), 20 were diploid, nine were triploid, one was tetraploid, and one was a neuploid. As to the correlation between morphology and data of FCM, tw o PMs were reclassified as HA, and eight HAs as PM, giving a ratio of 1 CM to 1.22 PM (23:28 cases). The incidence of HM was 1:265 pregnanci es, (CM, 1:587; PM, 1:483). Only one case (3.6%) of PM was suspected c linically, One specimen of persistent disease occurred following a dip loid CM. In our retrospective histological and FCM study in which 172 cases diagnosed as HM were retrieved from surgical pathology files bet ween 1981 and 1991, there were 129 CMs and 43 PMs (CMs:PMs = 3:1), The se findings indicate that PM is a common but underdiagnosed condition. Almost all studies in the literature may have severely under-reported the incidence of PM. It is suggested that during routine delivery and pathology examination only the most florid PMs are recognized, wherea s most with subtler changes go undiagnosed. Through detailed pathologi cal examination and data of FCM, an underdiagnosis of PM can be surely avoided. The recent elucidation of HM by FCM should lead to a complet e reappraisal of the epidemiology of gestational trophoblastic disease . Copyright (C) 1995 by W.B. Saunders Company