Gestational trophoblastic tumors (GTTs) comprise a wide spectrum of neoplastic disorders that arise from placental trophoblastic tissue after abnormal fertilization (Fig. 31-1). In the United States, GTTs account for fewer than 1% of all gynecologic malignancies. Their importance as an oncologic entity stems from the fact that they can often be cured with appropriate treatment, usually with the preservation of reasonable fertility with no adverse outcome. Even advanced-stage disease is potentially highly curable. Patients are classified into different prognostic groups on the basis of factors such as tumor histologic subtype, extent of disease, human gonadotropin titer, duration of disease, nature of the antecedent pregnancy, and extent of prior treatment. All patients should receive individualized management after careful prognostication under the care of a multidisciplinary team.
Gross specimen of two complete molar pregnancies. Note the absence of fetal tissue, which is replaced by abundant trophoblastic tissue.
GTTs are classified into two distinct groups: benign and malignant trophoblastic disease (1). Benign disease consists of a complete and partial hydatidiform mole or an invasive mole. Malignant disease comprises nonmetastatic and metastatic gestational trophoblastic disease. A hydatidiform mole is confined to the uterine cavity. Invasive moles and placental site tumors are locally invasive but rarely metastatic. Both tumors are rare, but they can be distinguished histologically (2). Choriocarcinomas are highly malignant and tend to metastasize extensively.
The hydatidiform mole is the most common type of GTT. It is essentially a benign condition with variable potential for malignant transformation. Most molar pregnancies resolve spontaneously after uterine evacuation, with no further event or adverse outcome. At any time during or after gestation, however, approximately 10 to 20% undergo malignant transformation to invasive nonmetastatic or metastatic trophoblastic disease. Nearly two-thirds of these lesions develop into persistent nonmetastatic gestational trophoblastic disease, while the remaining one-third develop distant metastases (3,4). In the 1950s, a woman with choriocarcinoma had a less than 5% chance of survival. With improved understanding of the natural history and prognostic factors of this disease and the development of a reliable tumor marker for diagnosis (the beta subunit of human chorionic gonadotropin, or β-hCG) as well as effective chemotherapy for treatment, even advanced metastatic gestational trophoblastic disease is associated with a cure rate of greater than 90% (5).
In the United States, GTTs develop in approximately 1 in 1000 to 2000 pregnancies (6-8). Overall, approximately 80% of GTTs are hydatidiform moles, 15% are invasive moles, and 5% are choriocarcinomas. Choriocarcinoma is associated with an antecedent mole in 50% of the cases, a history of abortion in 25%, term delivery in 20%, and ectopic pregnancy in 5% (9).
Molar pregnancies are reported in approximately 3000 patients per year, and malignant transformation occurs in 6 to 19% of these ...