[1085] Early Complete Hydatidiform Mole: A Clinicopathologic and Flow Cytometric Study of 270 Cases

M Fukunaga. Jikei University Daisan Hospital, Komaeshi, Tokyo, Japan

Background: With the increased use of ultrasound complete hydatidiform mole (CM) is being diagnosed at increasingly early stages of gestation. Thus, the classic features of CM may be lacking and CM can be easily misdiagnosed as partial mole (PM) or hydropic abortion (HA).
Design: Between 1981 and 2008, 270 cases of early CM (6-12 weeks' gestation, mean: 9.1 weeks) were identified at Jikei University Hospital and its affiliated hospitals. Clinicopathologic features of early CMs were examined. 210 cases were also analyzed by DNA flow cytometry (FC) using formalin-fixed, paraffin-embedded tissue blocks.
Results: Patients ages ranged from 18 to 49 years (mean: 29.1 years). Histologically, villi showed diffuse or focal stromal edema with bulbous or clubbed outlines and focal to circumferential trophoblastic hyperplasia. Villous stroma was hypercellular with capillary networks and karyorrhectic debris was observed. No stromal fibrosis was observed. Extravillous intermediate trophoblasts showed atypia. There were no fetal parts or amnion. Two patients had twins with CM. These cases were histologically characterized by two populations of villi, one with non-edematous stroma and another with edema and moderate trophoblastic hyperplasia. No nucleated red blood cells were observed except in the two cases of twins. Substantial cases were initiallly diagnosed as PM. By DNA FC, 155 cases were diploid, 29 tetraploid and 26 (non-triploid or non-tetraploid) aneuploid. There were no histologic differences among the diploid, tetraploid and aneuploid CMs. In the follow-up information, 14 of 73 diploid CMs (19.2%) and 4 of 18 tetraploid CMs (22.2%) had invasive mole, and one each with diploid and tetraploid CMs developed choriocarcinoma. None of 18 patients with aneuploid CM had sequelae.
Conclusions: Early CMs have somewhat different histologic features than classical second-trimester CMs. The histologic features include: 1) bulbous or clubbed villi, 2) focal or diffuse villous edema, 3) focal to circumferential trophoblastic hyperplasia, 4) cellular villous stroma with capillary networks and karyorrhectic debris, 5) no stromal fibrosis, 6) atypia of extravillous intermediate trophoblasts. Early CMs can be easily misdiagnosed as PM because of less prominent villous edema and mild form of trophoblastic hyperplasia. There were no histologic differences among the diploid, tetraploid and aneuploid CMs. DNA FC is helpful in equivocal cases. Aneuploid CMs are associated with lower risk for persistent disease than diploid or tetraploid CMs.
Category: Gynecologic & Obstetrics

Tuesday, March 23, 2010 1:00 PM

Poster Session IV # 130, Tuesday Afternoon


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