Abstract： Objective:To explore the value of T2-weighted imaging(T2WI),diffusion weighted imaging(DWI)and mean apparent diffusion coefficient(mADC)combined with cancer antigen 125(CA125)in the differential diagnosis of uterine sarcoma and atypical leiomyoma.Materials and Methods:From January 2011 to February 2023,59 patients with uterine sarcoma and 118 patients with atypical leiomyomas confirmed by pathology in our hospital were retrospectively analyzed.The imaging features of T2WI and DWI(including signal intensity of T2WI and DWI,maximum tumor diameter,mADC value)and clinical relevant information(including age,clinical symptoms,menopausal status and serum CA125)were collected.Mann-Whitney U test and chi-square test were used for univariate analysis,and then logistic regression was used to construct models based on T2WI,DWI sequence and serum CA125 alone or in combination.The receiver operating characteristic(ROC)curve was used to evaluate the performance of the prediction model,and the area under the curve(AUC),sensitivity and specificity of the model were calculated.Results:The preoperative serum CA125 levels in the uterine sarcoma group were significantly higher than those in the atypical leiomyoma group(P=0.043).On T2WI and DWI sequences,the solid component of uterine sarcoma showed more hyperintensity than that of atypical leiomyoma,and the mADC value was significantly lower than that of atypical leiomyoma(all P＜0.001).The optimal preoperative cut-off value for serum CA125 used to identify the two was 23.41 U/mL,and the optimal cut-off value for mADC was 1.165×10-3 mm2/s.The combination of T2WI,DWI,mADC values and serum CA125 resulted in an AUC of 0.981,a sensitivity of 98.3%and a specificity of 92.4%(P＜0.001).Conclusions:T2WI and DWI sequences combined with serum CA125 can be used as an effective method to distinguish uterine sarcoma from atypical leiomyoma.