Evaluation of CT findings for the differentiation of benign from malignant primary retroperitoneal tumors

Background Benign and malignant primary retroperitoneal tumors （RT） have different pathological manifestations,and overlapping imaging characteristics.This study aimed to evaluate the value of computed tomography （CT） for differentiating benign from malignant RT.Methods One hundred and ninety-four patients with clinical and radiographic data were evaluated retrospectively following surgical resection of primary RT.There were 38.1％ （n=74） benign lesions and 61.9％ （n=120） malignant lesions.Categorical variables were tested with a chi-square test or Fisher＇s exact test for the diagnostic indexes and sensitivity and specificity of CT characteristics.Results In univariate analysis,the differences in ill-defined margins,irregular surfaces,long diameter ＞6.75 cm,short diameter ＞6.25 cm,and solid or mixed texture had statistical significance; the sensitivity and specificity were 44.2％ and 91.9％,70.0％ and 62.2％,68.8％ and 60.7％,59.7％ and 74.2％,87.5％ and 35.1％,respectively.In multivariate analysis,a combination of all the above indexes was the best model for differentiating malignant tumors,resulting in the most accurate diagnosis of malignancies with a sensitivity of 77.2％ and a specificity of 81.1％ （P＜0.0001） when the score was 4.The differences in other findings including CT attenuation,number,and calcification had no statistical significance.The unique characteristics included the spotted enhancement （mottled high density）in schwannoma （P＜0.0001）,adipose tissue in liposarcoma （P＜0.0001）and paravertebral location in neurogenic tumors （P＜0.0001）.Conclusions More accurate differential diagnosis of primary RT can be made through comprehensive analysis of the combined diagnostic indexes of CT.Some specific characteristics of CT can assist in preoperative planning.