Gestational Trophoblastic Disease
Summary of Key Points
Incidence and Epidemiology
• The incidence of complete hydatidiform mole is approximately 1 in 1200 pregnancies in the United States.
• The incidence of partial hydatidiform mole is approximately 1 in 650 pregnancies.
• Repeat moles occur in approximately 1 in 125 pregnancies, and third moles occur in approximately 1 in 5 pregnancies.
• Complete hydatidiform mole is usually due to an androgenetic diploid conception, in which a haploid sperm fertilizes an egg that lacks female chromosomes.
• A partial hydatidiform mole develops when dispermy occurs, and the resulting conceptus is triploid.
Pathology
• Earlier diagnosis of complete hydatidiform mole due to improved ultrasound and human chorionic gonadotropin (hCG) assays has made the pathological diagnosis of complete hydatidiform mole more difficult because of its resemblance to partial hydatidiform mole and nonmolar abortions.
• Hydatidiform mole is characterized by hydropic villi with trophoblastic hyperplasia.
• Invasive mole is characterized by invasion of myometrium by hydropic villi surrounded by hyperplastic trophoblasts.
• Choriocarcinoma is characterized by sheets of neoplastic cytotrophoblasts and syncytiotrophoblasts invading tissue and is associated with necrosis and hemorrhage. Hematogenous spread occurs early.
• Placental site and epithelioid trophoblastic tumors are rare forms of choriocarcinoma made up of mononuclear cells from intermediate trophoblast at the implantation site that invade the myometrium. Both placental site and epithelioid trophoblastic tumors metastasize late and are relatively resistant to chemotherapy.
Clinical Features
• Hydatidiform mole commonly presents in the first trimester with vaginal bleeding.
• Complete hydatidiform mole is usually diagnosed by ultrasound because of the abnormal appearance of the placenta and the absence of a fetus.
• Partial hydatidiform mole can be difficult to diagnose by ultrasound and is usually confirmed pathologically.
• Persistent postmolar gestational trophoblastic neoplasia is usually nonmetastatic and is characterized by a rising hCG level and persistent bleeding due to residual molar tissue.
• Metastatic postmolar gestational trophoblastic neoplasia (GTN) usually involves the lungs and, rarely, the brain, liver, and other distant sites.
• The diagnosis of gestational trophoblastic neoplasia after a miscarriage or term pregnancy is frequently delayed and commonly presents with significant disease.
