Objective: To examine the immunoexpression of indoleamine 2,3-dioxygenase (IDO) in gestational trophoblastic neoplasia (GTN), including hydatidiform moles and gestational trophoblastic tumors.
Study design: GTN cases were identified from a referral center for trophoblastic disease, and sections were immunostained with anti-IDO antibody and classified as positive or negative for trophoblast staining relative to normal chorionic villi.
Results: Fifty-two cases were included: 10 nonmolar hydropic miscarriages (HA), 11 partial moles (PHM), 9 complete moles (CHM), 15 choriocarcinoma cases (CC) and 7 placental site trophoblastic tumors (PSTT). All HA, PHM and CHM demonstrated IDO staining; 2 of 15 CC were strongly positive, 6 demonstrated focal positivity (< 10% of tumor cells), and the remainder were negative. Of the 7 PSTT, only 2 showed focal weak positivity; the others were negative.
Conclusion: Hydatidiform moles express IDO, but the majority of gestational trophoblastic tumors, despite arising from villous or nonvillous trophoblast, do not express this enzyme, suggesting that IDO-mediated immunoregulation is unlikely to be a major component of the malignant phenotype in these tumors. Immunotherapeutic approaches involving IDO might represent ancillary approaches in a minority of patients with GTN.