General Information About Gestational Trophoblastic Tumors and Neoplasia
Gestational trophoblastic tumors (GTTs) and neoplasias (GTNs) are rare but highly curable tumors arising from the products of conception in the uterus.
- Placental-site trophoblastic tumor (very rare).
- Epithelioid trophoblastic tumor (even more rare).
- Persistence of complete or partial gestational hydatidiform moles.
- Invasive moles.
All of these entities are grouped under the term gestational trophoblastic disease (GTD). The reported incidence of GTD varies widely worldwide, from a low of 23 per 100,000 pregnancies (Paraguay) to a high of 1,299 per 100,000 pregnancies (Indonesia). However, at least part of this variability is caused by differences in diagnostic criteria and reporting. The reported incidence in the United States is about 110 to 120 per 100,000 pregnancies. The reported incidence of choriocarcinoma, the most aggressive form of GTT, in the U.S. is about 2 to 7 per 100,000 pregnancies. The U.S. age-standardized (1960 World Population Standard) incidence rate of choriocarcinoma is about 0.18 per 100,000 women between the ages of 15 years and 49 years.
Two factors have consistently been associated with an increased risk of GTD:
- Maternal age.
- Prior history of hydatidiform mole (HM).
If a woman has been previously diagnosed with an HM, she carries a 1% risk of HM in subsequent pregnancies. This increases to approximately 25% with more than one prior HM. The risk associated with maternal age is bimodal, with increased risk both for mothers younger than 20 years and older than 35 years (and particularly for mothers >45 years). Relative risks are in the range of 1.1 to 11 for both the younger and older age ranges compared to ages 20 to 35 years. However, a population-based HM registry study suggests that the age-related patterns of the two major types of HM—complete and partial HM (see Cellular Classification section below)—are distinct. In that study, the rate of complete HM was highest in women younger than 20 years, then decreasing monotonically with age. However, the rates of partial HM increased for the entire age spectrum, suggesting possible differences in etiology. The association with paternal age is inconsistent. A variety of exposures have been examined, with no clear associations found with tobacco smoking, alcohol consumption, diet, and oral contraceptive use.