Gestational Trophoblastic Disease
Question No. 2. The Answer is: (D) Y-chromosome.
Discussion: This is an epithelioid trophoblastic tumor (ETT). Differential diagnoses include keratinizing squamous cell carcinoma, placental site trophoblastic tumor, placental site nodule and epithelioid smooth muscle tumor. It resembles an invasive squamous carcinoma from the cervix (SCC). Unlike SCC, ETT is positive for cytokeratin 18. Both can present with abnormal vaginal bleeding. 50% of ETTs contain Y-chromosome as it can be derived from a male conceptus. Unlike SCC of the cervix, the pathogenesis of ETT has not been directly linked to HPV infection.
In ETT, the serum b-hCG levels are nearly always elevated at the time of diagnosis, although it is usually not very high (usually under 2500miu/ml). Beta-hCG levels can therefore be used to monitor treatment. ETT generally shows focal hPL and CD 146 staining, while placental site trophoblastic tumor shows diffuse hPL and CD146 positivity. ETTs are generally positive for AE1/AE3, EMA, EGFR, E-cadherin and alpha-inhibin. Smooth muscle markers such as desmin would characterize epithelioid smooth muscle tumor but are negative in ETT.