PDCD1 and gestational trophoblastic neoplasm: In this study, we investigated the expression of PD-1, lymphocyte activation gene-3 (LAG-3), T cell immunoglobulin-3 (TIM-3), and galectin-9 (GAL-9) in the TIIs of human GTN specimens and analyzed the correlation between expression difference and prognosis of GTN patients to explore potential new targets for immunotherapy of drug-resistant and recurrent GTN.