Which histological feature best distinguishes gestational choriocarcinoma from hydatidiform mole and invasive mole?

• A Presence of circumferential trophoblastic proliferation around oedematous villi
• B Predominance of intermediate trophoblast infiltrating between smooth muscle fibres
• C Invasion of myometrium by villi retaining their vascular core
• D Complete absence of chorionic villi with biphasic sheets of cytotrophoblast and syncytiotrophoblast ✓

Explanation

Choriocarcinoma is a malignant epithelial tumour showing a dimorphic population of atypical cytotrophoblast and syncytiotrophoblast without any formed chorionic villi, accompanied by haemorrhage and necrosis. Villous structures persist in hydatidiform mole and invasive mole, which rules out option A and C respectively. Option B describes placental site trophoblastic tumour. Choriocarcinoma characteristically spreads early by the bloodstream, especially to the lungs.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

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