Discrepancy between radiological and pathological size of renal masses

OBJECTIVE To investigate the differences between tumor sizes measured by preoperative computed tomography (CT) imaging and pathologic examination of surgical specimens in Chinese patients who received extirpative surgery for renal tumors. METHODS From September 2008 to September 2010, 204 patients with renal tumors treated in the Renji Hospital were enrolled in this study, and their clinicopathological data were collected and analyzed. The paired Student's t-test was used to compare the mean radiological tumor maximum diameter and the mean pathological tumor maximum diameter. All cases in which post-operative down-staging or up-staging occurred due to the discrepancy between radiological and pathological tumor maximum diameters were identified. In addition, the relationship between radiological and pathological tumor maximum diameters and histological subtypes was analyzed. RESULTS Overall, the radiological mean maximum diameter of tumors on CT was 48.3 mm and the pathological mean maximum diameter was 47.0 mm. On average, CT overestimated pathological size by 1.3 mm (P = 0.018). CT overestimated pathological tumor size in 111 (54.4%) patients, underestimated in 71 (34.8%) patients and equal pathological size in 22 (10.8%) patients. Among the 190 patients with pT1 or pT2 tumors, there was a discrepancy between clinical and pathological staging in 35 (18.4%) patients. Of these, 29 (15.3%) patients were down-staged post-operatively and 6 (3.2%) were up-staged. When subjects were categorized according to radiographic tumor size associated with clinical stage, statistically significant difference (average of 1.76 mm) was observed between radiographic and pathologic maximum diameters ranging 41-70 mm (P = 0.035). For clear cell carcinoma, mean radiographic tumor maximum diameter was significantly larger than the pathologic maximum diameter by 1.69 mm (P = 0.003). CONCLUSIONS There is a statistically significant but small difference (1.3 mm) between mean radiological and mean pathological tumor maximum diameters. For some patients, this difference leads to a discrepancy between clinical and pathological staging, which may have implications on pre-operative clinical decision and prognosis prediction.