To explore the CT imaging features of primary renal rare malignant tumors.

From Dec. 2008 to Oct. 2018, 18 patients with primary renal rare malignant tumors pathologically proven lesions after operation who had CT exams with contrast were enrolled in our hospitals. The CT imaging features of all tumors were analyzed respectively.

18 malignant tumors were malignant fibrous histiocytoma (MFH,n=1), renal leiomyosarcoma (RLMS,n=1), invasive renal parenchyma urothelial carcinoma (IRPUC,n=1), cystic renal cell carcinoma (CRCC,n=6), chromophobe renal cell carcinoma (CPRCC,n=9) respectively. MFH with unclear border showed heterogeneous density with patchy necrosis on CT precontrast and slight delayed enhancement. RLMS with clear border showed heterogeneous density with patchy necrosis on CT precontrast and slight delayed enhancement. IRPUC showed multiple lesions with heterogeneous density on CT precontrast and slight heterogeneous enhancement. CRCC showed cystic lesions on CT precontrast. Various degrees of septum and floc enhancement were detected after intravenous administration of contrast material. CPRCC showed mixed isodensity and hypodensity on CT precontrast followed by slight/moderate delayed enhancement (n=6) or washout enhancement (n=3). The diagnostic accuracy rate of CT for renal rare malignant tumors was 72.2%(13/18).

Special CT imaging characteristics for primary renal rare malignant tumors had certain value for diagnosis and preoperative assessment. However, the finial diagnosis still depends on pathology.