Objective:To investigate the expression,function,and clinical significance of CD24 in testicular germ cell tumors(TGCT).Methods:This study included 204 testicular germ cell tumor(TGCT)patients from the TCGA database and the TGCT-Changhai testicular germ cell tumor cohort(Changhai Hospital cohort).Prognostic analysis and multivariate analysis were employed to evaluate the association between CD24 expression and clinical characteristics.Immunohistochemistry(IHC)staining of tumor tissues was used to elucidate the mechanism by which CD24 regulated the tumor immune microenvironment(TIME)in TGCT.Finally,by analyzing the diffrences in PD-L1 expression levels and tumor-associated macrophage(TAM)M2-type cell infiltration rates between CD24 high-expression and low-expression groups,and employing the TIDE algorithm,we investigated the correlation between CD24 expression levels and immune escape scores as well as immunotherapy response rates.Results:Analysis of the TCGA database revealed that CD24 expression was significantly upregulated in TGCT with high clinical staging and M-stage(P<0.05).Compared to adjacent normal tissues,CD24 expression was significantly elevated in both primary and metastatic TGCT tissues(P<0.05).Significant differences in CD24 expression levels were observed across TNM stages and tumor progression statuses(all P<0.05).Univariate logistic regression analysis identified CD24 as a predictive factor for clinical outcomes in TGCT patients(OR=0.135,95%CI[0.035,0.516],P=0.003),and multivariate analysis further confirmed its role as an independent predictor(OR=0.057,95%CI[0.005,0.624],P=0.019).In TGCT tissues,CD24 mRNA levels correlated with immune cell markers CD206 and CD70(all P<0.05).Additionally,CD24 expression levels demonstrated significant predictive value in immune escape scoring and immunotherapy response rate assessments.Conclusions:CD24 is highly expressed in TGCT tissues and its expression is significantly correlated with the prognosis of TGCT patients,which makes it a potential new target point of biotherapy for testicular germ cell tumor patients.