Comparative study of MRI appearances in clear cell renal cell carcinoma,papillary renal cell carcinoma and chromophobe renal cell carcinoma

Abstract

Objective To investigate the differential diagnostic features of subtypes of renal cell carcinoma(RCC) using dynamic contrast-enhanced MRI(DCE-MRI).Methods The MRI appearances of 77 RCCs, including 55 clear cell RCCs(CCRCC),14 papillary RCCs(PRCC) and 8 chromophobe RCCs(CRCC), were retrospectively analyzed and compared with findings of pathology. DCE-MRI was conducted in each case after intravenous administration of contrast agent. Region of interest measurements (cortical, nephrographic and delayed Phases) of signals within tumor and uninvolved renal cortex were used to calculate percentage signal intensity change and tumor-to-cortex enhancement index, and the data was analyzed by AVONA and t test. Results On unenhanced and enhanced MRI, most CRCCs showed homogeneous signal(7/8). CCRCC and PRCC often show inhomogenous signal with necrosis(36/55, 7/14). Hemorrhage and cystic degeneration were often found in PRCC (9/14). On the cortical, nephrographic and delayed phase images, CCRCCs showed greater signal intensity change[(296.15±60.27)%, (236.33±58.31)% and (216.83±46.72)%,respectively than PRCCs (79.70±18.84)%, (122.81±27.35)% and (117.55±20.63)%, respectively], and CRCCs showed intermediate change [(119.56±40.76)%, (163.06±33.91)% and (179.72±32.89)%, respectively].A phenomenon of quick staining and quick fainting was observed in CCRCCs. Both of CRCCs and PRCCs showed delayed enhancement. The tumor-to-cortex enhancement index at the cortical, nephrographic and delayed phases was highest for CCRCCs (1.26±0.34, 0.92±0.23 and 0.76±0.14, respectively), lowest for PRCCs (0.33±0.12, 0.41±0.23 and 0.35±0.11, respectively), and intermediate for CRCCs (0.54±0.10, 0.62±0.15 and 0.69±0.12, respectively,P＜0.01). The degree of enhancement was significantly different among the 3 subtypes at the every contrast enhanced phase (F=940.931, 124.515 and 38.194, P＜0.01), so was the tumor-to-cortex enhancement index(F=798.625,78.308 and 73.699, P＜0.01). There was a good consistency between MR appearances of the 3 RCC subtypes and pathological characteristics. Conclusion DCE-MRI could distinctly show imaging features of CCRCC, PRCC and CRCC, which were related to their pathological characteristics, and these features were helpful in predicting a specific subtype of RCC. Key words: Renal cell carcinoma, subtype; Differential diagnosis; Magnetic resonance imaging