Invasive Mole and Choriocarcinoma
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Direct answer
Invasive mole and choriocarcinoma are both gestational trophoblastic neoplasias that secrete hCG and respond well to chemotherapy. The key histological difference is that invasive mole retains chorionic villi invading the myometrium, whereas choriocarcinoma consists of malignant trophoblast without villi. Choriocarcinoma is more prone to haematogenous metastasis, most often to the lungs.
What you must remember
- Histology: Invasive mole shows villi invading the myometrium; choriocarcinoma shows sheets of cyto- and syncytiotrophoblast without villi.
- Antecedent pregnancy: Invasive mole follows a hydatidiform mole, while choriocarcinoma follows a mole, abortion or term pregnancy, with about half following a mole.
- hCG: Both show markedly raised serum hCG, which is used for diagnosis, staging and follow-up.
- Metastasis: Choriocarcinoma most often spreads to the lungs, with the vagina, liver and brain as other sites.
- Risk score: The FIGO 2000 score uses age, antecedent pregnancy, interval from the index pregnancy, hCG level, largest tumour size, metastatic sites, number of metastases and prior failed chemotherapy.
- High-risk cut-off: A FIGO score of 7 or more defines high-risk disease.
- Low-risk drug: Single-agent methotrexate with folinic acid rescue is standard for low-risk disease.
- High-risk regimen: Multi-agent chemotherapy such as EMA-CO is used for high-risk disease.
A stepwise approach from diagnosis to follow-up
Gestational trophoblastic neoplasia is managed by a fixed sequence: confirm, stage, score, treat and follow. Each step decides the next, so the risk score determines the intensity of chemotherapy.
- Confirm the diagnosis: Histology separates invasive mole from choriocarcinoma, and serum hCG confirms active trophoblastic disease. Villi within the myometrium point to invasive mole.
- Stage the disease: Chest imaging and pelvic imaging define local and pulmonary spread. Brain imaging is added when symptoms or high-risk features suggest metastasis.
- Score the risk: The FIGO 2000 score is calculated from age, antecedent pregnancy, interval from the index pregnancy, hCG, largest tumour size, metastatic sites, number of metastases and prior failed chemotherapy. The total places the patient into low or high-risk groups.
- Treat low-risk disease: Single-agent methotrexate with folinic acid rescue is the standard approach. Actinomycin D is used as an alternative when methotrexate is unsuitable.
- Escalate for high-risk disease: Multi-agent regimens such as EMA-CO are used. Surgery or radiotherapy may be considered for resistant or localised disease in selected patients.
- Follow up with hCG: Serum hCG is monitored until it normalises and stays normal for a set period. Contraception is advised during follow-up so that a new pregnancy does not confuse the hCG pattern.
Common traps in trophoblastic questions
Questions here test histology, the risk score and the first-line regimen.
- Trap: Calling a lesion with myometrial villi choriocarcinoma. Correct: Villi in the myometrium indicate invasive mole, whereas choriocarcinoma contains no villi.
- Trap: Assuming choriocarcinoma follows only a molar pregnancy. Correct: It can follow an abortion or a term pregnancy, so raised hCG after any pregnancy needs evaluation.
- Trap: Giving single-agent therapy to every patient. Correct: High-risk disease by FIGO score needs multi-agent chemotherapy such as EMA-CO.
Frequently asked questions
What is the main histological difference between invasive mole and choriocarcinoma?
Invasive mole contains chorionic villi that invade the myometrium, whereas choriocarcinoma consists of malignant trophoblast without villi. Both are gestational trophoblastic neoplasias and both secrete hCG. Histology is therefore the key to separating invasive mole from choriocarcinoma.
Which pregnancy outcomes can precede choriocarcinoma?
Choriocarcinoma can follow a hydatidiform mole, an abortion or a term pregnancy, and about half of cases follow a mole. Any pregnancy followed by persistent bleeding or raised hCG needs evaluation for trophoblastic disease. Early recognition of choriocarcinoma improves the chance of cure.
How does the FIGO 2000 score guide chemotherapy in gestational trophoblastic neoplasia?
The FIGO 2000 score uses age, antecedent pregnancy, interval from the index pregnancy, hCG level, largest tumour size, metastatic sites, number of metastases and prior failed chemotherapy. A score of 7 or more classes gestational trophoblastic neoplasia as high risk and calls for multi-agent chemotherapy such as EMA-CO. Lower scores are usually treated with single-agent methotrexate.
Where does choriocarcinoma most often metastasise?
Choriocarcinoma most often metastasises to the lungs, while the vagina, liver and brain are other common sites. Haematogenous spread explains the predominance of lung metastases. Staging therefore includes chest imaging, and brain imaging is added when symptoms suggest it.
Why is serum hCG monitored after invasive mole or choriocarcinoma treatment?
Serum hCG is monitored after treatment to detect persistent or recurrent trophoblastic disease. Treatment is considered complete only after hCG has normalised and remained normal for a set period. Contraception is advised during follow-up so that a new pregnancy does not mask the hCG pattern.