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Commonly used synonyms[edit]

Gestational trophoblastic disease (GTD) may also be called gestational trophoblastic tumour (GTT).

Hydatidiform mole (one type of GTD) may also be called molar pregnancy.

Persistent disease; persistent GTD: If there is any evidence of persistence of GTD, usually defined as persistent elevation of beta hCG (see «Diagnosis» below), the condition may also be referred to as gestational trophoblastic neoplasia (GTN).^[5]

Types[edit]

GTD is the common name for five closely related tumours (one benign tumour, and four malignant tumours):^[6]

• The benign tumour
  • Hydatidiform mole

Here, first a fertilised egg implants into the uterus, but some cells around the fetus (the chorionic villi) do not develop properly. The pregnancy is not viable, and the normal pregnancy process turns into a benign tumour. There are two subtypes of hydatidiform mole: complete hydatidiform mole, and partial hydatidiform mole.

• The four malignant tumours
  • Invasive mole
  • Choriocarcinoma
  • Placental site trophoblastic tumour
  • Epithelioid trophoblastic tumour

All five closely related tumours develop in the placenta. All five tumours arise from trophoblastic cells. The trophoblast is the membrane that forms the wall of the blastocyst in the early development of the fetus. In a normal pregnancy, trophoblastic cells aid the implantation of the fertilised egg into the uterine wall. But in GTD, they develop into tumour cells.

Incidence[edit]

Overall, GTD is a rare disease. Nevertheless, the incidence of GTD varies greatly between different parts of the world. The reported incidence of hydatidiform mole ranges from 23 to 1299 cases per 100,000 pregnancies. The incidence of the malignant forms of GTD is much lower, only about 10% of the incidence of hydatidiform mole.^[7] The reported incidence of GTD from Europe and North America is significantly lower than the reported incidence of GTD from Asia and South America.^{[8][9][10][11]} One proposed reason for this great geographical variation is differences in healthy diet in the different parts of the world (e.g., carotene deficiency).^[12]

However, the incidence of rare diseases (such as GTD) is difficult to measure, because epidemiologic data on rare diseases is limited. Not all cases will be reported, and some cases will not be recognised. In addition, in GTD, this is especially difficult, because one would need to know all gestational events in the total population. Yet, it seems very likely that the estimated number of births that occur at home or outside of a hospital has been inflated in some reports.^[13]

Risk Factors[edit]

Two main risk factors increase the likelihood for the development of GTD: 1) The woman being under 20 years of age, or over 35 years of age, and 2) previous GTD.^[14][15][16]

Although molar pregnancies affect women of all ages, women under 16 years of age have a six times higher risk of developing a molar pregnancy than those aged 16–40 years, and women 50 years of age or older have a one in three chance of having a molar pregnancy.^[17]

Being from Asia/of Asian ethnicity is an important risk factor.^[18]

The ABO blood groups of the parents appear to be a factor in choriocarcinoma development, i.e. women with blood group A have been shown to have a greater risk than blood group O women.

Diagnosis[edit]

Cases of GTD can be diagnosed through routine tests given during pregnancy, such as blood tests and ultrasound, or through tests done after miscarriage or abortion.^[19] Vaginal bleeding, enlarged uterus, pelvic pain or discomfort, and vomiting too much (hyperemesis) are the most common symptoms of GTD. But GTD also leads to elevated serum hCG (human chorionic gonadotropin hormone). Since pregnancy is by far the most common cause of elevated serum hCG, clinicians generally first suspect a pregnancy with a complication. However, in GTD, the beta subunit of hCG (beta hCG) is also always elevated. Therefore, if GTD is clinically suspected, serum beta hCG is also measured.

The initial clinical diagnosis of GTD should be confirmed histologically, which can be done after the evacuation of pregnancy (see «Treatment» below) in women with hydatidiform mole.^[20] However, malignant GTD is highly vascular. If malignant GTD is suspected clinically, biopsy is contraindicated, because biopsy may cause life threatening haemorrhage.

Treatment[edit]

Treatment is always necessary.

The treatment for hydatidiform mole consists of the evacuation of pregnancy.^{[21][22][23][24][25]} Evacuation will lead to the relief of symptoms, and also prevent later complications.Suction curettage is the preferred method of evacuation. Hysterectomy is an alternative if no further pregnancies are wished for by the female patient. Hydatidiform mole also has successfully been treated with systemic (intravenous) methotrexate.^[26]

The treatment for invasive mole or choriocarcinoma generally is the same. Both are usually treated with chemotherapy. Methotrexate and dactinomycin are among thechemotherapy drugs used in GTD.^{[27][28][29][30]} Only a few women with GTD suffer from poor prognosis metastatic gestational trophoblastic disease. Their treatment usually includes chemotherapy. Radiotherapy can also be given to places where the cancer has spread, e.g. the brain.^[31]