Correlation of pathology with tumor size of renal masses

The current standard of care for radiographically identified enhancing renal lesions is surgical removal. However, some of these lesions prove to be benign and did not truly warrant extirpation. Mass size has been traditionally described as a parameter to predict the malignant potential. We compiled our experience with surgically treated renal masses and correlated lesion size with final pathology.

We performed a retrospective analysis of extirpative renal surgery and resultant renal mass pathology from 1998- January 2006. Nephrectomies performed for non-malignant disease or transitional cell carcinomas were excluded. Renal tumors were staged by the 2002 TNM classification system.

Three hundred ninety-four patients with 460 lesions were identified. Overall, 24% of masses were determined to be benign and 76% were malignant. Three hundred forty-three malignant lesions were renal cell carcinoma (98%). Masses were stratified by size. Two hundred thirty masses were smaller than 4 cm and 72 (31.3%) of these were benign. There were 166 lesions between 4 cm and 7 cm with an 18% benign rate. Sixty-four lesions were > 7 cm in size. Only eight of these were benign (12.5%). Chi square testing revealed the 31.3% benign rate of the < 4 cm group to be significantly different than the benign rates of the other groups.

The preponderance of renal lesions removed for benign pathology occurs when lesion size is small, typically less than 4 cm. This information may be useful in deciding to offer expectant management of an otherwise surgical lesion in a patient who is a poor candidate to undergo an operative procedure.