Renal tumors and the risk of malignancy based on size.

Purpose: To determine the incidence of malignancy in resected renal tumors in a subpopulation of Canadian patients and the significance of tumor size, patient's demographics, and whether the tumor was an incidental finding.

Methods: Medical records of 168 consecutive nephrectomies performed between March 2003 and June 2008 at our institution were reviewed retrospectively.

Results: Average age of the patients was 61 years old (SD 11, range 28-89) and male to female ratio was 1.3:1. Total of 180 masses were resected in 168 nephrectomies (128 radical, 40 partial) during the study period. Of the 180 masses, 20 (11%) were benign and 160 (89%) were malignant lesions. Fifty-five percent of the resected renal masses were incidentally found on preoperative imaging. Based on the pathology reports, the average size of the masses was 5.5 cm (SD 4.0, range 0.3-25.0). The larger masses were more likely to be malignant than the smaller masses (Pearson's chi-square test, p = 0.040).

Conclusion: The present study assists us to adequately assess the risk of malignancy of a renal mass in a Canadian population based on size which allows us to properly advise the patients and suggest best possible treatment options. We recommend more aggressive therapies for masses larger than 4 cm and parenchymal sparing procedures for masses smaller than 4 cm as large proportion of these are benign.