Gestational trophoblastic disease
How an abnormal fertilisation with too much paternal genetic material makes the trophoblast overgrow into a molar pregnancy, why very high hCG causes its features, and how trophoblastic tissue can persist, invade and spread.
By the end, you can
- Describe normal trophoblast, its controlled invasion and its production of hCG.
- Explain how complete and partial moles arise from abnormal fertilisation, and why excess paternal genome drives trophoblast overgrowth.
- Compare complete and partial moles in genetics, appearance and risk of persistent disease.
- Relate the clinical features of a molar pregnancy to swollen villi and very high hCG.
- Distinguish invasive mole, choriocarcinoma and placental site trophoblastic tumour, and explain why hCG tracks residual disease.
What it is
Gestational trophoblastic disease (GTD) is a group of conditions in which placental trophoblast grows abnormally after a conception. It includes the hydatidiform moles (complete and partial), abnormal pregnancies with swollen villi and excess trophoblast, and the gestational trophoblastic neoplasms: choriocarcinoma, placental site trophoblastic tumour and epithelioid trophoblastic tumour. Clinically, gestational trophoblastic neoplasia (GTN) also includes invasive mole and any trophoblastic disease that persists after a pregnancy ends.
5 types to tell apart
- Complete hydatidiform mole
- Diploid with only paternal chromosomes; no embryo; all villi swollen, with trophoblast proliferating all round them; very high hCG; the higher risk of persistent disease.
- Partial hydatidiform mole
- Triploid, with two paternal sets and one maternal set; an abnormal embryo or fetal tissue may be present; some villi swollen; lower hCG and lower risk.
- Invasive mole
- Molar villi grow into the myometrium or its vessels, and can reach the lungs or vagina; the villi are still present.
- Choriocarcinoma
- A malignant tumour of cytotrophoblast and syncytiotrophoblast without villi; bleeds, invades vessels early and spreads through the blood. It can follow a mole or any other pregnancy.
- Placental site and epithelioid trophoblastic tumours
- Rare tumours of the intermediate (extravillous) trophoblast; they make little hCG and grow more slowly.
US spelling: tumour → tumor.
Normal function
Trophoblast: invasive by design
After fertilisation, the outer cells of the blastocyst, the trophoblast, attach to the endometrium and become the fetal part of the placenta. They form two layers over each : an inner layer of dividing cytotrophoblast and an outer, multinucleated syncytiotrophoblast, which bathes in maternal blood in the and makes human chorionic gonadotrophin (hCG).
A third population, the extravillous (intermediate) trophoblast, leaves the tips of anchoring villi and invades the and the inner , remodelling the . This invasion is normal but tightly limited in depth and time.
A normal conception has one set of chromosomes from the egg and one from the sperm. Some genes are imprinted, active only from one parent: broadly, paternally expressed genes favour growth of the placenta, and maternally expressed genes restrain it. The balance between the two sets keeps trophoblast growth in check.
Underlying change · Step 1 of 5
Too much paternal genome
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 8 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Underlying change · Step 2 of 5
Overgrown trophoblast and swollen villi
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 8 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Disrupted function · Step 3 of 5
Very high hCG and its effects
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 8 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Disrupted function · Step 4 of 5
When molar tissue invades
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 8 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Consequences · Step 5 of 5
Choriocarcinoma and other trophoblastic neoplasms
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 8 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Symptoms and signs
Symptoms, signs and findings
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 8 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Recap
Recap
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 8 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Self-check
Check your understanding
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 8 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .