OBJECTIVE:

To determine the level of infiltration and antigen profile of immune cells and explore their relationship in intraplacental and postmolar choriocarcinoma to better understand the immunobiology of choriocarcinoma.

STUDY DESIGN:

Immunolocalization of CD8, Granzyme B (GrB) and FoxP3 was performed on sections prepared from 5 intraplacental and 7 postmolar choriocarcinomas to characterize effector Tc cells (GrB+, CD8+) and GrB- (GrB-, CD8+) Tc cells, GrB+ NK cells (GrB+, CD8-) and Treg (FoxP3+) cells.

RESULTS:

In the case of intraplacental choriocarcinoma, immune cell infiltration was not detected in the surrounding villi or in the tumor. Immune cell infiltration into the implantation site of the placenta with intraplacental choriocarcinoma did not differ from that into the normal pregnancy implantation site. In postmolar choriocarcinoma the immune cell infiltration of the adjacent tissue was vigorous and involved all types of immune cells (Tc, NK, Treg). In 6 of 7 cases of postmolar choriocarcinoma, in spite of the vigorous immune response, immune cells could not be seen in the choriocarcinoma tissue. A sharp infiltration border of immune cells was noted at the edge of the postmolar choriocarcinoma tissue.

CONCLUSION:

Intraplacental choriocarcinoma is not associated with a vigorous immune cell response. In contrast, postmolar choriocarcinoma is associated with a vigorous immune cell response in adjacent tissues but not the choriocarcinoma tissue itself.