How Does The Radiographic Size Of A Renal Mass Compare With The Pathologic Size?

Several reports in the past have suggested that there can be measurable differences between the measured size of renal masses as imaged radiographically, and the size of the renal mass measured by the pathologist on the resected surgical specimen. Hypotheses as to why this difference might exist have suggested that the disruption of blood flow to these highly vascular tumours may be responsible. Here, Schlomer and colleagues examine differences in renal tumour size when measured clinically (radiographically) versus pathologically.

The authors examined 133 renal masses identified in 126 patients. All patients had a CT scan within 60 days of surgery (median 29 days, range 1-60). Of note, 90.2% of the masses were renal cell carcinoma. Looking at all 133 tumours together, there was no difference in the average clinical size (4.5 cm) when compared to the average pathologic size (4.1 cm, p=0.35). However, in breaking down the population of patients, the investigators noted that for patients with renal tumours between 1 and 5 cm in diameter, there was a significant difference between the measured clinical and pathologic size of the tumours. The largest difference was noted in tumours that were 4-5 cm in size, where the average clinical size was 0.87 cm larger than the average pathologic size (p=0.025). The largest percentage difference between clinical and pathologic size was noted in tumours that were 1-2 cm in diameter. The average clinical size was 21.1% larger than the average pathologic size (p=0.005).The authors conclude that CT may overestimate the size of a renal mass relative to pathologic size, and that this fact should be considered in weighing the merits of a nephron sparing approach in a given patient. Given that tumour size is less and less a variable to consider in partial nephrectomy, where anatomy and tumour location appear to be most important, I would question the clinical significance of these small differences in measured tumour volume between CT and resected specimens.(Source: Urology : December 2006.)