Renal oncocytoma and carcinoma: failure of differentiation with CT.

The authors studied the hypothesis that oncocytoma and adenocarcinoma of the kidney can be differentiated with computed tomographic (CT) criteria and that differences would become more apparent as tumors enlarged. On contrast material-enhanced scans, homogeneous attenuation throughout the tumor and a central, sharply marginated, stellate area of low attenuation were considered predictors of oncocytoma. Any area of decreased attenuation in the tumor except for a stellate, central area was used as a predictor of adenocarcinoma. Among oncocytomas larger than 3 cm in diameter, 67% exhibited the criteria for oncocytoma and 33% met the criterion for adenocarcinoma; among smaller oncocytomas, the respective results were 82% and 18%. Among adenocarcinomas larger than 3 cm in diameter, 84% fulfilled the criterion for malignancy and 16% were incorrectly predicted to be oncocytomas; among smaller adenocarcinomas, the respective results were 58% and 42%. The authors conclude that the CT criteria used are poor predictors of the diagnosis of oncocytoma or adenocarcinoma regardless of tumor size.