A Multi-institutional Study on Histopathological Characteristics of Surgically Treated Renal Tumors: the Importance of Tumor Size

Abstract

Purpose: The incidence of accidentally detected small renal tumors is increasing throughout the world. In this multiinstitutional study performed in Korea, histopathological characteristics of contemporarily surgically removed renal tumors were reviewed with emphasis on tumor size. Materials and Methods: Between January 1995 and May 2005, 1,702 patients with a mean age of 55 years underwent surgical treatment at 14 training hospitals in Korea for radiologically suspected malignant renal tumors. Clinicopathological factors and patient survival were analyzed. Results: Of the 1,702 tumors, 91.7% were malignant and 8.3% were benign. The percentage of benign tumors was significantly greater among those 4 cm (13.2%) than those > 4 cm (4.5%) (p < 0.001). Among renal cell carcinoma patients, the percentage of tumors classed as stage T3 was significantly less among tumors 4 cm (5.2%) than those > 4 cm (26.8%) (p < 0.001). The percentage of tumors classed as Fuhrman's nuclear grades 3 was also significantly less among tumors 4 cm (27.3%) than tumors > 4 cm (50.9%) (p < 0.001). The 5-year cancerspecific survival rate was 82.7%, and T stage (p < 0.001), N stage (p < 0.001), M stage (p = 0.025), and Fuhrman's nuclear (p < 0.001) grade were the only independent predictors of cancer-specific survival. Conclusion: In renal tumors, small tumor size is prognostic for favorable postsurgical histopathologies such as benign tumors, low T stages, and low Fuhrman's nuclear grades. Our observations are expected to facilitate urologists to adopt function-preserving approach in the planning of surgery for small renal tumors with favorable predicted outcomes. Key Words: Kidney neoplasms, renal cell carcinoma, nephrectomy, surgical pathology