Solid Renal Cortical Tumors: Differentiation with CT

Abstract

PURPOSE: To retrospectively determine if solid renal cortical tumors can be differentiated on computed tomographic (CT) images on the basis of their morphologic features and enhancement patterns. MATERIALS AND METHODS: Institutional review board approval was obtained and the informed consent requirement was waived for this HIPAA-compliant study. Between January 2004 and September 2005, 193 consecutive patients (age range, 19-95 years; 112 men, 81 women) with renal masses underwent total or partial nephrectomy and preoperative renal CT. Two radiologists retrospectively reviewed CT studies in an independent and blinded fashion. The pattern and degree of enhancement, lesion contour, presence of neovascularity, and calcifications were evaluated. Fisher exact tests, Pearson chi(2) tests, multivariate logistic regression, and Wilcoxon rank sum tests were performed. RESULTS: Of the 198 renal tumors (median size, 3.4 cm; range, 1.1-20.0 cm) included in this study, 108 (55%) were clear cell renal cell carcinomas (RCCs); 30 (15%), papillary lesions; 24 (12%), chromophobe adenomas; 14 (7%), oncocytomas; six (3%), lipid-poor angiomyolipomas; and 16 (8%), other or unclassified renal tumors. Clear cell RCC most commonly manifested with a mixed enhancement pattern of both hypervascular soft-tissue components and low-attenuation areas that corresponded to necrotic or cystic changes (reader 1, 88% of clear cell tumors; reader 2, 79% of clear cell tumors). This pattern was highly predictive of clear cell RCC (odds ratio of 22 and 54 for readers 1 and 2, respectively, for comparison with homogeneous pattern), whereas the homogeneous and peripheral enhancing patterns were more predictive of less aggressive papillary and chromophobe lesions. Clear cell RCCs and oncocytomas tended to be hypervascular, chromophobe lesions and angiomyolipomas tended to enhance moderately, and papillary lesions were mostly hypovascular. CONCLUSION: Certain imaging features and the degree of enhancement may be helpful in differentiating subtypes of renal cortical tumors.