Gestational trophoblastic disease

Introduction

Gestational Trophoblastic Disease (GTD) is a rare group of interrelated tumors that develop from the cells that would normally form the placenta during pregnancy. In a healthy pregnancy, trophoblastic cells help the fertilized egg implant in the uterine wall and form the placenta, which nourishes the developing fetus. However, in GTD, there is an abnormal proliferation of these trophoblastic cells, leading to tumor growth inside the uterus.

While the diagnosis can be devastating, particularly for women who were hoping for a normal pregnancy, GTD is one of the most curable of all solid tumors. Even in cases where the disease spreads beyond the uterus (metastatic disease), cure rates exceed 90% with modern chemotherapy.

This article provides a detailed, evidence-based overview of Gestational Trophoblastic Disease, covering its types, visual characteristics, symptoms, diagnosis, and treatment options.

Understanding the Types of GTD

GTD is not a single disease but a spectrum of disorders. It is broadly divided into two main categories: Hydatidiform Moles (HM) (which are benign, though pre-malignant) and Gestational Trophoblastic Neoplasia (GTN) (which are malignant or potentially malignant).

1. Hydatidiform Moles (Molar Pregnancies)

This is the most common form of GTD. It occurs when there is a genetic error during fertilization. Instead of a viable fetus, the placental tissue grows into a mass of fluid-filled cysts resembling a “bunch of grapes.” There are two subtypes:

• Complete Mole: In a complete mole, there is no fetal tissue. It usually occurs when a sperm fertilizes an “empty” egg (a nucleus-free egg). The paternal chromosomes duplicate, resulting in a karyotype of 46, XX (or rarely 46, XY), but all genetic material is paternal. The risk of developing into cancer (GTN) is approximately 15-20%.
• Partial Mole: In a partial mole, there is usually some abnormal fetal tissue present, but the fetus cannot survive. It typically occurs when two sperm fertilize a normal egg, resulting in 69 chromosomes (triploidy) instead of the usual 46. The risk of progression to GTN is lower, about 1-5%.

2. Gestational Trophoblastic Neoplasia (GTN)

This refers to the malignant forms of the disease. These can arise after a molar pregnancy, a normal term pregnancy, a miscarriage, or an ectopic pregnancy.

• Invasive Mole: This is a hydatidiform mole that invades the muscle wall of the uterus (myometrium). It is locally aggressive but rarely metastasizes.
• Choriocarcinoma: A highly malignant tumor that can spread rapidly through the blood to distant sites, most commonly the lungs, liver, brain, and vagina.
• Placental Site Trophoblastic Tumor (PSTT): A very rare, slow-growing tumor that develops at the site where the placenta attached to the uterus. It tends to remain in the uterus for a long time and is often resistant to chemotherapy.
• Epithelioid Trophoblastic Tumor (ETT): An extremely rare variant similar to PSTT.

How Does It Look?

The visual presentation of GTD varies significantly depending on the type and stage of the disease. Understanding “how it looks” involves both the clinical appearance (what a doctor sees on imaging) and the histopathological appearance (what a pathologist sees under a microscope).

Macroscopic Appearance (Clinical/Imaging View)

In a classic molar pregnancy, the uterus is often larger than expected for the gestational age. On an ultrasound, a complete mole presents a distinctive “snowstorm” or “Swiss cheese” appearance. This is due to the swollen chorionic villi (the placental tissue) and areas of hemorrhage. There is no identifiable fetus or amniotic sac.

In a partial mole, the ultrasound may show a fetus with severe growth restriction or structural abnormalities, alongside a thickened placenta with cystic spaces.

For GTN (like choriocarcinoma), the appearance is different. The tumor is typically a dark red, hemorrhagic, and necrotic mass invading the uterine wall. It is highly vascular, meaning it bleeds easily. If it has metastasized to the vagina, lesions appear as dark purple or blue nodules, often referred to as “blueberry lesions.”

Histopathological Appearance (Microscopic View)

Under a microscope, the features are distinct:

• Complete Mole: Pathologists see diffuse swelling of the chorionic villi (hydropic degeneration) and abnormal overgrowth of the trophoblast cells (hyperplasia). There are no fetal blood vessels.
• Partial Mole: There is a mixture of large, swollen villi and small, fibrotic villi. The trophoblastic overgrowth is focal (localized) rather than diffuse. Fetal red blood cells (nucleated RBCs) may be visible.
• Choriocarcinoma: Unlike moles, choriocarcinoma lacks the normal villous structure. It consists of sheets of abnormal trophoblast cells (cytotrophoblasts and syncytiotrophoblasts) invading muscle and blood vessels, accompanied by massive hemorrhage and necrosis.

Table 1: Visual Comparison of Common GTD Types

Symptoms

The symptoms of GTD often mimic those of a normal pregnancy or a miscarriage, which can make early diagnosis challenging. However, certain “red flags” should prompt immediate medical investigation.

The “Classic” Symptoms of a Molar Pregnancy

Historically, the textbook symptoms included severe vomiting, rapid uterine enlargement, and passing grape-like cysts vaginally. However, due to modern early ultrasound technology, most molar pregnancies are now diagnosed in the first trimester before these severe symptoms develop.

Common early symptoms include:

1. Vaginal Bleeding: This is the most common symptom, occurring in up to 84% of cases. The bleeding is often described as “prune juice” colored (dark brown) and may be intermittent or continuous. It results from the separation of the molar tissue from the uterine wall.
2. Severe Nausea and Vomiting (Hyperemesis Gravidarum): Because of extremely high levels of the hormone human chorionic gonadotropin (hCG), women with GTD often experience nausea and vomiting that is much more severe than typical morning sickness.
3. Abnormal Uterine Size: The uterus may be larger than expected for the date of the pregnancy (due to the rapid growth of molar tissue and blood clots) or, in some cases, smaller than expected.
4. Passage of Tissue: In advanced cases, women may notice the passage of small, grape-like cysts from the vagina. This is diagnostic of a molar pregnancy.
5. Early Pre-eclampsia: Preeclampsia (high blood pressure and protein in the urine) usually occurs in the third trimester. If it presents before 20 weeks of gestation, it is highly suspicious for a molar pregnancy.
6. Hyperthyroidism Symptoms: Very high hCG levels can mimic thyroid-stimulating hormone (TSH), leading to symptoms of an overactive thyroid, such as a racing heart, sweating, and anxiety. This is rare but associated with large tumor burdens.
7. Pelvic Pain or Pressure: The rapid enlargement of the uterus or the presence of large ovarian cysts (theca lutein cysts, stimulated by high hCG) can cause abdominal pain or pressure.

Symptoms of Gestational Trophoblastic Neoplasia (GTN)

GTN can develop weeks or even years after a pregnancy event (molar pregnancy, miscarriage, or term birth). Symptoms vary based on the location and extent of the disease.

• Persistent Vaginal Bleeding: Bleeding that continues or recurs after a miscarriage, abortion, or normal delivery is a key warning sign.
• Symptoms of Metastasis: Because choriocarcinoma spreads via the blood, symptoms may arise in distant organs:
• Lungs: Cough, shortness of breath, chest pain, or coughing up blood.
• Brain: Headaches, seizures, dizziness, or stroke-like symptoms (weakness on one side of the body).
• Liver: Abdominal pain or jaundice (yellowing of the skin).
• Vagina: Painless, dark purple nodules that may bleed heavily if touched.
• Abdominal Swelling: Internal bleeding from a ruptured tumor or the development of large ovarian cysts can cause the abdomen to swell.
• PSTT/ETT Specific Symptoms: These rare types often present with absent periods (amenorrhea) or irregular vaginal bleeding long after a normal pregnancy. Since they produce lower levels of hCG, the classic signs of high hormones (like severe nausea) are often absent.

Table 2: Key Symptoms and Warning Signs

Diagnosis

If GTD is suspected, usually based on ultrasound findings and a positive pregnancy test, a series of tests are performed:

1. Pelvic Ultrasound: The primary imaging tool. It visualizes the “snowstorm” pattern of a complete mole or the abnormal placenta of a partial mole. It also evaluates the ovaries for theca lutein cysts.
2. Quantitative hCG Blood Test: A blood test measuring the exact level of hCG. In normal pregnancy, hCG levels plateau around 10-12 weeks. In GTD, levels are often significantly higher (often >100,000 mIU/mL). hCG is also used as a tumor marker to monitor the response to treatment.
3. Histopathology: The definitive diagnosis is made by examining the tissue under a microscope. Tissue is obtained via a Dilation and Curettage (D&C) procedure to evacuate the uterus.
4. Genetic Testing: If a partial vs. complete mole cannot be distinguished by microscopy, ploidy analysis (checking the number of chromosomes) can be performed.
5. Staging Workup: If GTN is diagnosed, further imaging (Chest X-ray, CT scan of the chest/abdomen/pelvis, or MRI of the brain) is required to determine if the disease has spread. This uses the FIGO staging system (Stages I-IV) and the WHO Prognostic Scoring System (low risk vs. high risk).

Treatment and Management

The treatment strategy depends heavily on whether the patient has a benign molar pregnancy or malignant GTN, and whether they wish to preserve fertility.

Treatment for Hydatidiform Mole (Molar Pregnancy)

• Suction Dilation and Curettage (D&C): This is the standard first-line treatment. Under anesthesia, the cervix is dilated, and the molar tissue is gently suctioned out of the uterus.
• hCG Monitoring: After evacuation, the hCG levels must be monitored weekly until they are undetectable for three consecutive weeks, then monthly for 6-12 months. This ensures the disease does not recur.
• Contraception: Pregnancy must be strictly avoided during the monitoring period (usually 6-12 months) because a new pregnancy would elevate hCG levels, making it impossible to distinguish between a normal pregnancy and a recurrence of GTD.

Treatment for Gestational Trophoblastic Neoplasia (GTN)

GTN is treated based on the FIGO risk score.

• Low-Risk GTN (Score 0-6):
• Treated with single-agent chemotherapy, usually Methotrexate or Actinomycin-D.
• Cure rates approach 100%.
• Treatment continues until hCG levels normalize, plus several “consolidation” cycles to prevent relapse.
• High-Risk GTN (Score ≥7):
• Treated with multi-agent chemotherapy, usually the EMA-CO regimen (Etoposide, Methotrexate, Actinomycin-D, Cyclophosphamide, Vincristine).
• This is an intensive regimen requiring hospitalization or frequent clinic visits.
• Cure rates are 80-90%.
• Placental Site Trophoblastic Tumor (PSTT):
• These tumors are resistant to chemotherapy.
• Hysterectomy (surgical removal of the uterus) is the primary treatment, as the tumor tends to stay localized to the uterus.
• Surgery:
• Hysterectomy is an option for women who have completed their childbearing and have drug-resistant disease.
• Surgery may also be needed to control hemorrhage or remove isolated resistant metastatic tumors in the lungs or brain.
• Radiotherapy: Occasionally used for brain metastases.

Prognosis and Fertility

The prognosis for GTD is excellent. Even for women with widespread metastases, the majority are cured.

Fertility preservation is a major priority in GTD management. Because the primary treatment for molar pregnancies is suction D&C (which spares the uterus), and chemotherapy for GTN does not usually destroy the ovaries (eggs), most women retain their fertility after treatment.

Women are generally advised to wait 12 months after completing chemotherapy before trying to conceive. When they do conceive, there is a slightly increased risk (about 1-2%) of having a second molar pregnancy, so early ultrasound in future pregnancies is recommended.

Psychological Impact

A diagnosis of GTD carries a unique psychological burden. Patients experience the loss of a pregnancy simultaneously with a cancer diagnosis. The need for prolonged monitoring, fear of recurrence, and anxiety about future fertility can be overwhelming. Access to psychological support, support groups (such as those offered by cancer charities), and clear communication with the oncology team is a vital component of holistic care.

Conclusion

Gestational Trophoblastic Disease encompasses a spectrum of rare but highly treatable conditions arising from placental tissue. While the presentation can be frightening—often involving bleeding and the loss of a pregnancy—the advent of hCG tumor markers and effective chemotherapy regimens has transformed the outlook for these patients. Early diagnosis via ultrasound, meticulous hCG surveillance, and risk-stratified treatment are the cornerstones of success. With modern management, the overwhelming majority of women with GTD, even in advanced stages, can expect a complete cure and the possibility of future healthy pregnancies.

References

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