Question
Trophoblastic tumors
Answer
Gestational trophoblastic tumours/diseases are a spectrum of proliferative trophoblastic lesions arising from placental tissue, ranging from benign to highly malignant:
1. Hydatidiform mole (benign):
- Complete mole: 46,XX, entirely paternal, diffuse hydropic villi, no fetal tissue, diffuse trophoblastic hyperplasia; “bunch of grapes” gross appearance; higher risk of progression to choriocarcinoma.
- Partial mole: Triploid, focal hydropic change, fetal tissue present, focal trophoblastic hyperplasia; lower malignant potential.
2. Invasive mole: A complete mole that penetrates (invades) the myometrium or its vessels, may embolize to distant sites (e.g., lung) but retains villous structure and does not have the aggressive metastatic behaviour of choriocarcinoma; usually responds well to chemotherapy.
3. Choriocarcinoma (malignant):
- A highly malignant tumour of trophoblastic epithelium (both cytotrophoblast and syncytiotrophoblast) with NO chorionic villi.
- May arise following a molar pregnancy (most common antecedent), normal pregnancy, abortion, or ectopic pregnancy.
- Gross: Soft, haemorrhagic, necrotic mass invading the myometrium.
- Microscopy: Sheets of anaplastic cytotrophoblast admixed with syncytiotrophoblast, with extensive haemorrhage and necrosis, marked vascular invasion.
- Very high serum β-hCG.
- Widely and early metastasizing (haematogenous spread, especially to lungs, brain, liver) but exquisitely chemosensitive with excellent cure rates even with metastases.
4. Placental site trophoblastic tumour (rare): Composed of intermediate trophoblast, secretes relatively little hCG but human placental lactogen (hPL); generally indolent but can be locally invasive.
All forms are monitored using serial serum β-hCG levels, which serve as an excellent tumour marker for diagnosis, treatment response, and surveillance.