Definition. A spectrum of histologically distinct diseases originating from the placenta: partial and complete hydatidiform mole, choriocarcinoma, and placental-site trophoblastic tumor (PSTT).
Tumor marker. Serum levels of βhCG (β-human chorionic gonadotropin) are extremely accurate.
Hydatidiform moles
Incidence. Japan has the highest incidence of molar pregnancy (2.0/1,000 pregnancies versus 0.6–1.1 for Europe and North America). Variations in the worldwide incidence rates result in part from discrepancies between population-based data and hospital-based data.
Risk factors include maternal age >35 years (>2× increase), prior molar pregnancy (10× increase), long-term use of oral contraceptives (2× increase), and dietary deficiency (β-carotene, vitamin A).
Clinical presentation. Partial moles usually present as a missed abortion during the first or early second trimester. Normal or marginally elevated βhCG levels are common. Complete moles typically have abnormal vaginal bleeding (85%) that prompts a healthcare visit. Due to earlier detection, fewer than 10% of women will have anemia, hyperemesis gravidarum, or pre-eclampsia. Markedly elevated βhCG levels (>>100,000 mIU/mL) are characteristic.
Sonographic findings. Partial moles may be suspected by visualizing a fetus with focal cystic spaces in the placenta and an increase in the transverse diameter of the gestational sac. Complete moles classically have a “snowstorm” appearance of diffuse hydropic swelling without a fetus. First-trimester sonograms may be too early to distinguish small molar villi from degenerating chorionic villi.
Diagnosis of hydatidiform moles is made by histopathologic analysis. Partial moles have a non-viable fetus with malformations (syndactyly, hydrocephalus, growth restriction), variably hydropic (swollen) villi, and minimal trophoblastic hyperplasia. Complete moles have no fetal tissue and consist of diffusely hydropic villi (grape-like vesicles) with widespread trophoblastic hyperplasia. Immunostaining with p57 or ploidy analysis may be indicated in some equivocal cases.
Treatment. Electric vacuum aspiration (EVA; see Chapter 16
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