Impact of p53 immunostaining in predicting advanced or recurrent placental site trophoblastic tumors: a study of 12 cases

To identify an indicator that can predict tumor cell spread beyond the uterine corpus.

We studied clinicopathology and immunohistochemistry of 12 cases of PSTT. Two cases of epithelioid trophoblastic tumor (ETT) were included as reference cases. For immunohistochemistry, antibodies against Ki-67, p53, human chorionic gonadotropin (hCG), human placental lactogen (hPL), carcinoembryonic antigen (CEA, polyclonal antibodies; pCEA), carcinoembryonic antigen-related cellular adhesion molecule 1 (CEACAM1), and bcl-2 were used. PSTT cases were divided as confined and non-confined groups (CG and NCG, respectively). CG consisted of stage I cases with no evidence of recurrence during the follow-up, while NCG consisted of either advanced (stage II or higher) or recurrent stage I lesions.

Age, the interval from the latest pregnancy, serum hCG/hPL levels, tumor size, mitotic figures, Ki-67 labeling indices, and bcl-2 did not discriminate NCG from CG. CEACAM1 and CEA-related antigens as determined by polyclonal anti-CEA antibodies were specifically stained in PSTT cells, but they could not discriminate groups. p53 was positive in PSTT cells in NCG (6/6, 100%), while it was positive in only one case of CG (1/6, 16.7%), indicating a possible usefulness of p53 immunostaining in predicting an invasive or recurrent propensity of PSTT cells (p=0.015).

This finding also suggests the importance of p53 function in the biology of PSTT cells.