Gestational Tumors

Tumors arising from the placental chorionic villi (derived from the fetus) are generically termed "gestational trophoblastic disease." The benign form of this disorder is hydatidiform mole, and affected pregnancies are referred to as "molar pregnancies." The malignant counterpart is choriocarcinoma. Since choriocarcinoma may arise in molar pregancies (1 in 40 molar pregnancies), moles should be viewed with suspicion.

Hydatidiform Mole

Molar pregnancies are more common in younger (teenage) and older (40-50 years) mothers. The incidence varies regionally from 1 to 10 in 1000 pregnancies, with a relatively lower risk in the United States.

Moles may be complete or partial. In a complete mole, the chorionic villi are markedly swollen with poor or no vascularization. In a partial mole, only a portion of villi are affected and the remainder of the placenta is more normal in structure. In complete moles, there is no fetal development; partial moles may show some fetal parts.

Molar pregnancies present with rapid enlargement of the uterus and very high hCG levels. Twin pregnancies also present with uterine enlargement and hCG levels greater than expected for gestational age, but hCG will usually be higher in molar pregnancies. These findings should prompt an ultrasound examination, which will not show fetal parts in a molar pregnancy.

Ultrasound examination will usually be definitive. In some centers, several additional tests are used, including human placental lactogen (hPL) and serum vs. urine estrogen/progestins. A finding of decreased hPL with markedly elevated hCG suggests trophoblastic disease. The pattern of steroid hormone metabolites in serum vs. urine can also indicate whether fetal adrenals are present and functioning. If fetal adrenal products are not present, a molar pregnancy is suggested.

Molar pregnancies are followed after treatment by serial measurement of serum hCG. hCG levels should become undetectable within 2-3 months after removal of a mole (under normal circumstances, hCG becomes undetectable about 2 weeks after delivery). Persistently elevated hCG suggests residual mole or choriocarcinoma with metastases arising in the mole.

Invasive Mole/Choriocarcinoma

Invasive moles penetrate into and even through the uterine wall. They may also embolize through vessels to distant locations, but do not grow there (i.e., they are locally invasive but do not metastasize). The tumor responds well to chemotherapy and technically is benign, though it may cause considerable local damage or hemorrhage. Residual tumor is indicated by persistantly elevated serum hCG.

Choriocarcinoma is a rapidly-growing and widely-metastasizing tumor. 50% arise in hydatidiform moles; the remainder are evenly divided between previous abortions and normal pregnancies, with a few occurring in ectopic pregnancies and teratomas. Choriocarcinoma is associated with persistently elevated hCG during and after pregnancy or removal of a mole. Gestational choriocarcinomas are highly responsive to chemotherapy and patients are typically cured. Remission is confirmed by undetectable hCG in serial specimens.

Ectopic Pregnancy and Spontaneous Abortion Testing for Congenital Diseases
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Last modified: 1/20/97; Author: J. Harrison