Intraplacental choriocarcinoma in a term placenta

(A) In this macroscopic view of a partially fixed cross-section of a term placenta, oriented from amniotic cavity (ac) at the top to maternal basal plate (bp) at the bottom, a wedge-shaped gross lesion resembling a placental infarct is located beneath the chorionic plate.

(B) An unmagnified view of a histopathology slide corresponding to the lesion seen in (A) shows a placental infarct (I) surrounded by a rim of neoplastic trophoblasts.

(C) At high magnification, avillous malignant syncytiotrophoblasts and cytotrophoblasts having atypical nuclei (arrowheads) and scattered atypical (cruciform) mitotic figures (arrow) are adjacent to mature normal terminal villi (nv) covered by benign syncytiotrophoblasts at the rim of the infarct.