Radiographic versus pathologic size of renal tumors: implications for partial nephrectomy.

OBJECTIVES: To compare the radiographic size with the pathologic size of renal tumors to determine whether these two measurements vary significantly and to evaluate whether any differences in tumor size could have an impact on the decisions regarding partial nephrectomy.
METHODS: In 87 renal tumors excised by partial nephrectomy, the maximum transaxial tumor size on computed tomography (CT) was compared with its corresponding pathologic transverse size. Tumors were locally excised after vascular occlusion and hypothermia. The average size of the tumors selected for partial nephrectomy by preoperative CT scan was 3.4 cm (range 1.9 to 9.3). The difference between the CT size and pathologic size was correlated with the histologic type of the renal tumors.
RESULTS: Of the 87 tumors, 52 (60%) were classified as clear cell carcinoma and 35 (40%) as other histologic types (papillary, chromophobe, oncocytoma, and angiomyolipoma). Clear cell carcinomas decreased an average of 0.97 cm versus 0.39 cm for the other tumor types. Of 62 tumors greater than 3 cm on CT, 43 averaged 0.87 cm smaller at pathologic evaluation (36 clear cell and 7 other types) and 19 showed no significant (less than 0.5 cm) decrease in size (2 clear cell and 17 other histologic types). Of 30 tumors greater than 4 cm on CT, 22 clear cell carcinomas shrank more than 1 cm and 8 tumors displaying other histologic features showed no decrease in size.
CONCLUSIONS: For renal tumors measuring greater than 4 cm, a decrease in tumor size may help facilitate partial nephrectomy, especially for clear cell carcinomas that do not extensively involve major vascular structures or the collecting system.