Tumor Necrosis on Magnetic Resonance Imaging Correlates With Aggressive Histology and Disease Progression in Clear Cell Renal Cell Carcinoma

Magnetic resonance imaging (MRI) has been shown to successfully differentiate renal cell carcinoma subtypes. The purpose of this study was to assess whether (1) the morphologic features of clear cell renal cell carcinoma on MRI correlated with its histologic pattern and (2) MRI findings correlate with disease progression. We demonstrate that MRI evidence of necrosis, renal vein thrombosis, and retroperitoneal collaterals correlate with tumor clear cell percentage and disease progression. Objective: The study objective was to correlate the magnetic resonance imaging (MRI) features of clear cell renal cell carcinoma (ccRCC) with the histopathologic features and disease progression. Methods: Institutional review board approval for this retrospective study was obtained; patient consent was not required. The initial staging MRI scans of 75 patients with histologically confirmed ccRCC were retrospectively reviewed. The imaging was assessed by 2 radiologists for the presence of tumor necrosis, cystic degeneration, intracellular fat, hemorrhage, retroperitoneal collaterals, and renal vein thrombosis. Quantitative analysis for the MRI presence of intracellular lipid within tumors was performed. MRI findings were correlated with histopathologic findings of clear cell percentage, alveolar and tubular growth pattern, and disease progression. Statistical associations were evaluated with nonparametric univariable analyses and multivariable logistic regression models. Results: Correlation between MRI and histopathologic features was performed in 75 patients, whereas follow-up data were available for progression analysis in 68 patients. The presence of tumor necrosis, retroperitoneal collaterals, and renal vein thrombosis on MRI was significantly associated with a low percentage of tumor cells with clear cytoplasm (P < .01) and metastatic disease at presentation or disease progression (P < .01). At multivariable analysis, necrosis remained the only feature statistically associated with disease progression (P=.03; adjusted odds ratio, 27.7; 95% confidence interval, 1.4-554.7 for reader 1 and P=.02; adjusted odds ratio, 29.3; 95% confidence interval, 1.7-520.8 for reader 2). Conclusions: Necrosis in ccRCC on MRI correlates with the histopathologic finding of lower percentage of tumor cells with clear cytoplasm and is a poor prognostic indicator irrespective of tumor size. (C) 2014 Elsevier Inc. All rights reserved.