Abstract: Objective  To analyze the evaluation and application value of magnetic resonance diffusion-weighted imaging(MR-DWI) and multi-slice spiral CT(MSCT) in primary retroperitoneal overlying tumor(PRT). 
Methods  A retrospective study was conducted on the clinical data of 67 patients with primary retroperitoneal overlying tumors. A total of 45 cases were diagnosed as malignant by pathological examination(malignant group), 22 cases of benign lesions(benign group) were all given MR-DWI and MSCT examination, and the positive detection rate, negative detection rate, misdiagnosis rate, missed diagnosis rate, sensitivity, and specificity of different methods were observed and evaluation. 
Results  A total of 67 patients with primary retroperitoneal overlying tumors were diagnosed by pathology. The results showed that according to the origin of PRT lesions: 23 cases of neurogenic origin, 27 cases of mesenchymal tissue origin, 8 cases of germ cell origin, 7 cases of lymphoid tissue origin 2. The other 2 cases. According to the nature of the tumor: 45 cases were malignant and 22 cases were benign. The misdiagnosis rate and missed diagnosis rate of MR-DWI were lower than MSCT(P＜0.05). The AUC value of the area under the curve of MR-DWI is(0.988), the sensitivity was 93.33%, and the specificity was 86.36%. The AUC value of the area under the curve of MSCT was 74.80%, the sensitivity was 75.56%, and the specificity was 45.45%. 
Conclusion  MR-DWI is used for the diagnosis of primary retroperitoneal tumors. Its accuracy is higher than that of MSCT, and it can provide an objective basis for the differentiation of benign and malignant tumors.

Key words: retroperitoneal neoplasms, magnetic resonance imaging, pathology processes, diagnosis