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Gestational Trophoblastic Neoplasia

Valerie L Ward, MD
Mary C Frates, MD

August 19, 1994

Presentation

An 18-year-old (G1 P0) woman at 11.5 weeks gestation presented with an elevated serum beta-subunit human chorionic gonadotropin (b-hCG) level of 285,730 mIU/ml.

Imaging Findings

Sagittal Ultrasound
Transverse Ultrasound

Transabdominal ultrasound images (sagittal, transverse) show complex solid and cystic areas (arrows) filling the endometrial cavity of the uterus.

Differential Diagnosis

Hydatidiform mole is the most likely diagnosis due to the appearance of a moderately echogenic soft tissue mass with multiple small, cystic spaces filling the uterine cavity and the high serum b-hCG. Leiomyoma with cystic degeneration and a "missed abortion" (nonviable pregnancy) with hydropic changes of the placenta may also be considered in the differential. The b-hCG in these cases, however, should be negative or extremely low.

Diagnosis

Hydatidiform Mole

Discussion

Hydatidiform mole is the benign form of gestational trophoblastic neoplasia (GTN). Moles result from abnormal fertilization of an empty ovum by a sperm carrying two sets of paternal chromosomes. They occur in 1/1,200 to 1/2,000 pregnancies in the US (as compared to 1/100 pregnancies in the Far East). There is an increased incidence of moles in women at the end of their reproductive years.

Clinical suspicion for a molar pregnancy typically begins with marked elevation of serum b-hCG, the immunologic biologic marker for GTN. Less commonly, the patient may present with vaginal bleeding or an abnormally enlarged uterus. Sonographic appearance is as stated above. In 20-50% of patients, ultrasound will show enlarged ovaries with multiple theca lutein cysts.

Benign hydatidiform moles are distinguished from the malignant forms of GTN, namely invasive mole and choriocarcinoma, on the basis of behavior and pathology. Invasive moles extend beyond the uterine avity and invade the myometrium. Choriocarcinoma metastasizes widely to the liver, lungs, brain, bone, gastrointestinal tract, and skin.

Treatment of hydatidiform moles includes suction evacuation of the uterus and curettage of the endometrium to rule out myometrial invasion. Chest radiographs and/or chest CT are obtained to rule out metastatic disease. Postoperatively, serum b-hCG levels are monitored and chemotherapy is used for persistent GTN.

Ultrasound is used to differentiate GTN from a normal intrauterine pregnancy, to evaluate for parametrial involvement (theca lutein cysts), and to monitor response to therapy.

References

1. Callen P. Ultrasonography in Obstetrics and Gynecology. 3rd ed. Philadelphia: WB Saunders, 1994: 615-624.

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