Comparative analysis of radiologically measured size and true size of renal tumors.

PURPOSE: We evaluated the differences between radiologically measured size and pathologic size of renal tumors.
MATERIALS AND METHODS: The data from 171 patients who underwent radical or partial nephrectomy for a renal tumor at Ajou University Hospital were reviewed. Radiologic tumor size, which was defined as the largest diameter on a computed tomographic scan, was compared with pathologic tumor size, which was defined as the largest diameter on gross pathologic examination.
RESULTS: Mean radiologic size was significantly larger than mean pathologic size for all tumors (p=0.019). When stratified according to radiologic size range, mean radiologic size was significantly larger than mean pathologic size for tumors <4 cm (p=0.003), but there was no significant difference between the sizes for tumors 4-7 cm and >7 cm. When classified according to histologic subtype, mean radiologic size was significantly larger than mean pathologic size only in clear cell renal cell carcinomas (p=0.002). When classified according to tumor location, mean radiologic size was significantly larger than mean pathologic size in endophytic tumors (p=0.043) but not in exophytic tumors. When endophytic tumors were stratified according to radiologic size range, there was a significant difference between the mean radiologic and pathologic sizes for tumors <4 cm (p=0.001) but not for tumors 4-7 cm (p=0.073) and >7 cm (p=0.603).
CONCLUSIONS: Our results suggest that in planning a nephron-sparing surgery for renal tumors, especially for endophytic tumors of less than 4 cm, the tumor size measured on a computed tomography scan should be readjusted to get a more precise estimate of the tumor size.