Computed Tomography Characterization of Renal Cell Tumors in Correlation with Histopathology

RATIONALE AND OBJECTIVES: The authors distinguish the histomorphologic subtypes of renal cell tumors (RCTs) by computed tomography (CT). METHODS: In a consensus conference between radiologists, pathologists, and urologists, the CT criteria of the various subtypes of RCTs (clear cell, chromophilic cell, chromophobic cell renal carcinoma and oncocytoma) were established. Computed tomography scans of 65 resected RCTs were reevaluated independently by seven radiologists. Using a numerical scoring system, they first attempted to differentiate clear cell from nonclear cell RCTs. A further attempt then was made to classify each tumor into one of the four categories. RESULTS: The sensitivity for the diagnosis of clear cell RCT was 72.5% (213 of 294 true-positive findings) and 82% (132 of 161 true-positive findings) for the nonclear cell group. For tumors more than 3 cm in diameter the sensitivities were 80.25% for the clear cell group and 80.7% for the nonclear cell group. Specific differentiation into the four subtypes was not possible. Oncocytomas were classified correctly in only 6 of 49 observations (12.2%). CONCLUSIONS: Small clear cell tumors often fail to show the CT characteristics that would permit an accurate classification. In tumors measuring 3 cm or more, differentiation between clear cell and nonclear cell types by means of CT criteria is possible. Nevertheless, as RCTs show a great variation in appearance, a differentiation into subtypes of the nonclear cell RCTs cannot be accomplished by CT. Using a uniform examination protocol and spiral scanning technique, the sensitivity of CT in the diagnosis of the subtypes of RCTs may be able to be further increased. Some tumors, especially oncocytomas, undoubtedly will remain diagnostic dilemmas.