Diagnostic Value Of MRI For Primary Retroperitoneal Neoplasms

Objective: To investigate the value of MRI in the diagnosis and differential diagnosis of Primary Retroperitoneal Neoplasms(PRNs).Materials and Methods: The MRI findings from 77 patients with PRNs, which had been confirmed by surgical pathology, were retrospectively evaluated. Firstly we investigated the MRI appearance which were helpful for the location judgment of neoplasms and observed the morphologic features, signal characteristics and blood supply of the neoplasms to format a diagnosis with a comparison to pathological results. Then, the value of MRI in localizing PRNs, and discriminating benign from malignant PRNs, as well as estimation of pathological types of PRNs were analyzed.Results: In 77 patients, there were 45 cases with benign tumors(58.4%), including 6 cases of neurilemmomas, 6 cases of ganglioneuromas, 4 cases of benig paragangliomas, 1 case of neurofibroma, 11 cases of(hemo)lymphangiomas, 8 cases of teratomas, 3 cases of Castleman’s disease, 3 cases of leiomyomas, 2 cases of mucinous cystadenomas, and 1 case of inflammatory myofibroblastic tumor; while the other 32 cases with malignant tumors(41.6%), including 16 cases of liposarcomas, 7 cases of leiomyosarcomas, 6 cases of neuroblastomas, 1 case of malignant paraganglioma, 1 case of undifferentiated pleomorphic sarcoma and 1 case of inflammatory myofibroblastic sarcoma. According to pathological analysis, the larger, necrotic and hemorrhagic tumors with unclear boundary, infiltrated surrounding tissue and richer blood supply were inclined to be malignancy. The tumors with creeping growth, low blood supply or no hematoma were apt to be benign. The MRI has the accuracy of 92.2%(71/77) in localizing neoplasms, of 89.6%(69/77) in discriminating benign from malignant tumor and of 74%(57/77) in determining the pathological type. The sensitivity, specificity, positive predictive value(PPV) and negative predictive value(NPV) of the distribution of the sympathetic chain were 100%, 79.6%, 67.6% and 100% respectively on the diagnosis of neurogenic tumors. The sensitivity, specificity, PPV and NPV of the creeping growth pattern were 72.7%, 95.5%, 72.7%, 95.5% respectively on the diagnosis of hemangiolymphangiomas or lymphangioma. The sensitivity, specificity, PPV and NPV of the prensence of fat and(or) lipid were 95.8%, 100%, 100%, and 98.1% on the diagnosis of liposarcomas or teratomas. The sensitivity, specificity, PPV and NPV of mucous matrix were 77.8%, 91.5% and 73.7%, 93.1% respectively on the diagnosis of ganglioneuromas, neuroblastomas, and neurilemmomas. The sensitivity, specificity and PPV and NPV of necrosis are 75.0%, 93.8%, 69.2%, 95.3% respectively on the diagnosis of paraganglioma and leiomyosarcoma. In PRNs cases, rich blood supply was frequently found in poorly differentiated malignant tumors, paraganglioma, and the type of hyaline vascular Castleman’s disease, low blood supply was usually found in ganglioneuroma, and tumors without blood supply were only found as lymphangioma.Conclusion: MRI scan had a certain value of tumor localization, discrimination of benign from malignant tumor, and the estimation of pathological type of PRNs.