Abstract: Objective: To analyze the Clinical and pathological characteristics and MSCT manifestations of retroperitoneal stromal tumors,and investigate diagnostic value of MSCT for retroperitoneal stromal tumors.Methods: The clinical and CT date of 12 patients with retroperitoneal stromal tumors confirmed by operation and pathology were retrospectively reviewed.All patients underwent plain CT scans and contrast–enhanced CT scans before operation.Results: Among the 12 patients,7 were men and 5 were women,the ages ranged above 40 years old in 8 cases,mean age 55 years old.The major clinical symptom of the retroperitoneal stromal tumors were abdominal masses and bellyache.12 patients of retroperitoneal stromal tumors on CT showed retroperitoneal soft tissue masses,the biggest diameter of tumors ranged from 3.0 cm to 21.0 cm,mean 11.0 cm.The tumors were round or oval in 7 cases,irregular in 5cases.The tumors in 2 cases were uniform density on plain CT scans,1 case of uniform enhancement and 1 case of non-uniform linear enhancement on contrast—enhanced CT scans.10 cases showed unhomogeneous density on plain CT scans,low density necrosit in 10,hemorrhage in 2 and calcification in 2;moderate or remarkable enhancement was found in the parenchyma of the tumor,while no enhancement was found in the necrosis and cystic areas of the tumors on contrast—enhanced CT scans.There were benign tumour in 1,potential malignant tumours in 3 and malignant tumours in 8,metastases were found in 3 cases.In 12 cases,all were CD 117 positive,7 were CD 34 positive in immuinohistochemical test.Conclusion: The retroperitoneal stromal tumors usually involve middle-old,and clinical symptom is rare;the CT findings of the retroperitoneal stromal tumors display some characteristic signs and demonstrate the pathological features,which is very helpful in the diagnosis and differential diagnosis.