Epithelioid trophoblastic tumour (ETT) is derived from which cell type and what is its characteristic immunohistochemical marker profile?

• A Syncytiotrophoblast; strongly positive for β-hCG and PLAP
• B Chorion laeve-type intermediate trophoblast; p63+ and CD10− ✓
• C Villous cytotrophoblast; positive for Ki-67 and p53
• D Implantation-site intermediate trophoblast; hPL+ and p63−

Explanation

Epithelioid trophoblastic tumour (ETT) arises from chorion laeve-type intermediate trophoblast (in contrast to PSTT which arises from implantation-site intermediate trophoblast). IHC profile of ETT: p63 positive, CK18 positive, CD10 negative, hPL focally positive. PSTT is p63-negative and hPL-strongly positive. This distinction is clinically important as both are chemoresistant, but ETT tends to be even more chemoresistant and requires complete surgical resection.

Reference: Williams Obstetrics, 26th ed.

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