[973] Early Partial Hydatidiform Mole: A Clinicopathologic Study of 138 Cases

M Fukunaga. Jikei University Daisan Hospital, Tokyo, Japan

Background: The widespread use of ultrasound in the diagnosis and management of intrauterine fetal death has results in hydatidiform moles being evacuated earlier than before.
Design: Clinicopathologic features, morphology, and DNA ploidy of early (12 weeks vs. late > 12 weeks) partial hydatidiform moles (PMs) were studied. A total of 160 cases of PMs were identified in the surgical pathology files (37 from 1981-90; 123 from 1991-2007). The diagnosis of molar pregnancy was based on the pathologic criteria of Szulman and Surti (Am J Obstet Gynecol 1978;132:20-27).
Results: The patients' ages ranged from 17 to 43 (mean: 30) years. Mean gestational ages were 9.5 weeks for early PMs and 14.9 weeks for late PMs. Early PM was more common in 1991-2007 (115/123, 93%) than in 1981-1990 (23/37, 62%). Pre-evacuation diagnosis of hydatidiform mole was achieved in only 5 early and 1 late PMs. There were no significant differences in histology between early and late PMs, except that villi were smaller in early PMs and there was extensive stromal fibrosis in late PMs. Although differentiating early PM from early complete mole was relatively straightforward, there were early PM cases that were histologically indistinguishable from hydropic spontaneous abortion. On ploidy analysis, 70 of 80 early and 19 of 20 late PMs were triploid, 5 early PMs were aneuploid, and 5 early and 1 late PMs were diploid. No significant histologic differences were seen between the triploid and nontriploid PMs. Ploidy heterogeneity among PMs was suggested. None of 65 patients with early PM and 1 of 11 late triploid PMs developed persistent gestational trophoblastic disease.
Conclusions: Early PM has become more prevalent than it was previously. There was no significant difference in histology except for smaller villi in early PMs between early and late PMs. The diagnosis of PM should be based on pathologic examination, since most PMs still elude clinical detection. Ultrasound examination may not be sensitive enough to detect early PMs that have not fully evolved. Practically, histologic differentiation between PM and hydropic abortion is extremely difficult in some placental tissues, and follow-up with the measurement of serum or urine hCG titers is required in these cases. DNA ploidy analysis is useful in the evaluation of problem cases. The risk of persistent disease seems to be very low in the case of early PM.
Category: Gynecologic

Tuesday, March 10, 2009 1:00 PM

Poster Session IV # 157, Tuesday Afternoon