The effect of discrepancy between radiologic size and pathologic tumor size in renal cell cancer

To investigate the difference between preoperative radiologic tumor size (RTS) and postoperative pathologic tumor size (PTS) in patients who underwent nephrectomy for renal cell carcinoma. We retrospectively reviewed 257 patients who received preoperative computed tomography (CT) before radical or partial nephrectomy for renal cell carcinoma from January 2010 to May 2015 in Huashan Hospital, Shanghai. RTS was defined as the largest diameter of tumor measured by CT and PTS as the largest diameter of tumor measured in the surgical specimens. Among all subjects, mean RTS was larger than PTS (4.57 ± 2.15 vs. 4.02 ± 2.15 cm, P = 0.004) with a discrepancy of 0.55 cm. When the patients were categorized according to T stage, the mean RTS was greater than PTS in the following groups: ≤4 cm group (2.90 vs. 2.59 cm, P = 0.02), >4 and ≤7 cm group (5.08 vs. 4.38 cm, P < 0.0001), except for >7 cm (8.9 vs. 8.0 cm, P = 0.142). Among patients with clear cell RCC, the mean RTS was larger than the mean PTS (4.57 vs. 3.98 cm, P = 0.004), similar result was also seen in non-clear cell group (4.54 vs. 4.16 cm, P = 0.045). The mean RTS was larger than PTS for the approach of radical nephrectomy (RN) (5.26 vs. 4.64 cm, P = 0.01), but not for the partial nephrectomy (PN) (3.34 vs. 2.92 cm, P = 0.067). Of the 257 renal cancers, 76 tumors were down-staged when comparing radiographic and pathologic tumor maximal diameter. The proportion of down-staged tumors had no difference between different genders (P = 0.283), different surgery approaches (P = 0.102), and different pathology types (P = 0.209). In this study, we found that renal tumor size was overestimated by radiography compared with pathologic results, and the T staging of some tumors was down-staged. But for patients who underwent PN, there was no difference between RTS and PTS. These results suggested that the PN should be considered first for the T1b renal tumor when tumor size was close to 4 cm, while the recommendation level of PN for T1b tumor was grade B according to EAU guidelines.