Usefulness Of CT For The Differentiation Between Fat Poor Angiomyolipoma And Non-clear Cell Renal Cell Carcinoma

PurposeTo investigate the CT features that could differentiate fat poor angiomyolipoma from non-clear cell renal cell carcinoma for the improvement of its diagnostic accuracy.Materials and Methods1.This retrospective study included 17 cases of fat poor angiomyolipoma(5 men and 12 women;age range,34~76 years;mean age,(54.6±13.6)years),15 cases of papillary renal cell carcinoma(papillary RCC)(10 men and 5 women;age range,53~82 years;mean age,(67.1±8.5)years)and 14 cases of chromophobe renal cell carcinoma(chromophobe RCC)(7 men and 7 women;age range,32~82 years;mean age,(55.8±13.5)years),which data of patients retrieved from Tianjin Medical University General Hospital from Janurary 2008 to August 2017.And all patients had received nephrectomy.2.The morphological characteristics,unenhanced and contrast-enhanced CT features of the tumors were analyzed.The morphological characteristics included the maximum diameter of tumor,location of tumor center,angular interface,calcified component,the cystic,pseudocapsule,intra-tumoral vessels,coexisting classic angiomyolipoma,unenhanced attenuation,unenhanced tumor-kidney attenuation difference and homogeneity.And the unenhanced and contrast-enhanced CT features included unenhanced and contrast-enhanced attenuation values,the amount of washout.3.The predictive value of a CT finding was determined by binary logical regression analysis and receiver operator characteristic(ROC)curve was used to analyze the diagnostic accuracy.Results1.The maximum diameter of tumor,unenhanced high attenuation,angular interface,the cystic and coexisting classic angiomyolipoma had statistic significant difference between fat poor angiomyolipoma and papillary RCC with chromophobe RCC(P<0.05).Compared with the chromophobe RCC group,the fat poor angiomyolipoma group exhibited more exophytic location(P<0.05).Binary logical regression analysis revealed the significance of unenhanced high attenuation and angular interface for differentiating fat poor angiomyolipoma from papillary RCC and chromophobe RCC,the cystic from papillary RCC(P<0.05).2.The fat poor angiomyolipoma group had higher unenhanced attenuation value compared with the papillary RCC and chromophobe RCC groups(P<0.01).Fat poor angiomyolipoma showed prominent enhancement in the corticomedullary phase and a slight washout in the nephrographic phase,whereas papillary RCC and chromophobe RCC tumors showed gradually increased enhancement or prolonged enhancement over time and they more often peaked in the nephrographic phase.The amount of washout had statistic significant difference between fat poor angiomyolipoma and papillary RCC with chromophobe RCC(P<0.01).The amount of tumor enhancement in all phases of fat poor angiomyolipoma was significantly higher than papillary RCC(P<0.01),whereas only in corticomedullary phase was significantly higher than chromophobe RCC(P<0.05).ROC curve analysis revealed the diagnostic significance of combining the maximum diameter of tumor,unenhanced attenuation value,tumor attenuation value in the corticomedullary phase and the amount of washout for differentiating fat poor angiomyolipoma from papillary RCC and chromophobe RCC with a AUC,sensitivity and specificity of 0.984,100.0% and 93.3% versus 0.912,88.2% and 92.9%,respectively.ConclusionThe maximum diameter,unenhanced attenuation value,tumor attenuation value in the corticomedullary phase and the amount of washout of the tumors could be helpful to differentiate fat poor angiomyolipoma from non-clear cell renal cell carcinoma.The unenhanced high attenuation and angular interface increased the possibility of fat poor angiomyolipoma,whereas the cystic could be helpful to identify papillary RCC.