Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (282 page)

   Flow cytometry will demonstrate triploidy.

   A karyotype will demonstrate 69 XXY in most cases, 69 XXX, and rarely 69 XYY.

   Clinical Presentation

CHM
occurs in 1:1,000 pregnancies. It develops when an anucleate ovum is fertilized by one or two spermatozoa resulting in a diploid cell with two sets of paternal chromosomes (see eBook Figure 8-16D–F). Ninety percent are homozygous 46 XX; the rest are heterozygous, mostly 46 XY with few 46 XX.
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   Laboratory Findings

   HCG levels are increased, usually >100,000 mIU/mL.

   Endometrial curettings reveal grape-like transparent villi. A fetus is not present.

   Histology reveals villi with prominent cisterns, trophoblastic hyperplasia, and atypia particularly of the implantation site. A p57 immunostain is negative.

   Flow cytometry reveals diploid cells.

Following treatment
by evacuation of the molar pregnancy, the following laboratory studies should be performed to determine whether residual neoplastic trophoblasts persist. Risk for persistence includes increased maternal age, a longer interval from a previous pregnancy, and higher hCG levels.

   Serum hCG is used for diagnosis and management of both benign and malignant types. A persistently elevated or slowly declining level by the end of first trimester indicates persistent trophoblastic disease and the need for systemic therapy for invasive mole or choriocarcinoma (see below). An hCG level >500,000 mIU/L is virtually diagnostic.

   After evacuation of the uterus, hCG is negative by 40 days in 75% of cases. If the test is positive at 56 days, 50% have trophoblastic disease.

   Repeat hCG test every 1–2 weeks with clinical examination for 6 months. Disease remits in 80% without further treatment. Plateau or rise of titer indicates persistent disease. Chemotherapy is indicated if disease persists or metastasizes.

   A negative hCG test should be rechecked every 3 months for 1–2 years.