Histopathology of a hysterectomy specimen from a woman who had a hydatidiform mole evacuated 8 months ago shows molar chorionic villi with proliferating atypical trophoblast infiltrating deep into the myometrium and its blood vessels. What is the diagnosis, and which feature separates it from choriocarcinoma?

• A Invasive mole; the presence of identifiable chorionic villi ✓
• B Choriocarcinoma; the presence of syncytiotrophoblast
• C Invasive mole; invasion limited to the superficial third of myometrium
• D Placental site trophoblastic tumour; monomorphic cytotrophoblast population

Explanation

Invasive mole is defined by molar villi, together with proliferating atypical trophoblast, invading the myometrium or its vasculature. The defining distinction from choriocarcinoma is retention of chorionic villi; choriocarcinoma shows only biphasic cytotrophoblast and syncytiotrophoblast with central haemorrhage and necrosis, never villi. Placental site trophoblastic tumour consists of intermediate trophoblast at the implantation site without villi. Invasion depth alone does not define invasive mole.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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