Microscopic description and IHC:
The hematoxylin and eosin slide shows enlarged, avascular villi with cystic swelling and central cisternae. There is an irregular diffuse circumferential proliferation of trophoblasts. No fetal parts are seen.
A p57 stain is negative within the villous stromal cells and cytotrophoblasts, and strongly positive in the intermediate trophoblasts (which act as an internal control).
Discussion:
A complete mole is the most common form of gestational trophoblastic disease, and usually presents in the second trimester. Clinically, an increase in serum beta hCG, along with vaginal bleeding and a disproportionately enlarged uterus suggest this diagnosis.
Grossly, the typical picture of “grape-like” and swollen villi is seen and the entire specimen appears involved (as opposed to a partial mole).
In a partial mole, there is generally a biphasic population of both normal and hydropic villi, and fetal parts may be seen.
In a choriocarcinoma, although it may manifest with similar symptoms (increased hCG and vaginal bleeding), there would be no chorionic villi seen. Choriocarcinomas generally exhibit marked nuclear pleomorphism and a high mitotic rate. A complete mole increases the risk of developing choriocarcinoma.
An early, non-molar pregnancy would not have the gross findings of microscopic villi, and if it is present microscopically, it is only very mild. Central cisternae are generally not seen.
Hydropic abortus is also very high on the differential diagnosis. p57 will be positive in the cytotrophoblast and negative in the syncytiotrophoblast.