Correlation between Radiologic and Pathologic Tumor Size in Localized Renal Cell Carcinoma

PURPOSE To evaluate the accuracy of radiologic tumor size for making decisions regarding nephron-sparing surgery of localized renal cell carcinomas (RCCs), we compared tumor size measured by a preoperative radiologic modality with that measured in the pathologic specimen. MATERIALS AND METHODS Between January 2003 and December 2007, a total of 186 patients with pT1 or pT2 RCC underwent radical or partial nephrectomy at our institute. We excluded 11 patients who had preoperative arterial embolization (n=9) or positive surgical margins (n=2), and a total of 175 patients were included in this study. Radiologic size was defined as the largest diameter on computed tomography (CT), and pathologic size was defined as the largest diameter of the surgical specimen of the tumor. We retrospectively analyzed the difference between radiologic and pathologic tumor size. RESULTS The radiologic and pathologic tumor sizes did not significantly differ (4.98+/-2.82 cm vs. 4.55+/-2.70 cm, respectively, p=0.152). In the subgroup analysis, the size difference was statistically significant only for tumor sizes of less than 6 cm. The size difference was largest in tumors of 3 to 4 cm, for which mean the radiologic size was 0.63+/-1.19 cm larger than the mean pathologic size (p=0.002). Histologic type had no significant influence on the difference between radiologic and pathologic size. CONCLUSIONS The tumor size of RCCs in preoperative CT seems to correlate well with pathologic tumor size. However, CT imaging may overestimate the size of a tumor in the small mass group (less than 6 cm). These results should be considered when making decisions about nephron-sparing surgery.