Contemporary imaging of patients with a renal mass: does size on computed tomography equal pathological size?

Objective: To evaluate the difference between radiographic size on computed tomography (CT) and the pathological size of renal tumours, in contemporary patients.
Patients and Methods: We retrospectively reviewed the records of 521 patients undergoing surgical resection of a renal mass between 2000 and 2007, who had tumour sizes recorded from both preoperative CT and pathological evaluation of the tumour specimen. Data on histological tumour type were also extracted. The paired Student's t-test was used to compare the mean radiographic size as measured on CT with the mean pathological size, with P < 0.05 considered to indicate statistical significance.
Results: For all patients, the mean radiographic size and mean pathological size was 4.79 and 4.69 cm, respectively (P = 0.02). Therefore, on average, radiographic size overestimated pathological size by 1 mm. In patients with a tumour of 4-7 cm, radiographic size overestimated pathological size by 0.21 cm (P = 0.007). However, there was no significant difference in patients with a tumour of <4 cm or >7 cm.
Conclusions: Using contemporary patients, there was a statistically significant overestimation of renal tumour sizes by CT compared with the pathological assessment. However, the overall difference between radiographic and pathological tumour size was 1 mm, suggesting that CT provides an accurate method with which to estimate renal tumour size.