Objective: To determine the number of lymph nodes that need to be examined to accurately stage the pN variable in patients undergoing radical nephrectomy (RN) for renal cell carcinoma (RCC).
Patients and methods: We reviewed the operative and pathology reports of 725 patients with RCC submitted for RN. All tumours were classified using the fifth edition of the Tumour-Nodes-Metastasis classification. For each patient the number of lymph nodes removed was recorded. The patients were divided into five different groups according to the number of nodes removed, i.e. group 1, 1-4; group 2, 5-8; group 3, 9-12; group 4, 13-16; and group 5, >or= 17. We evaluated the factors that affected the number of lymph nodes removed with nodal dissection and the variables that influenced the incidence of nodal involvement.
Results: Lymphadenectomy was performed in 608 patients (83.8%); in these patients the rate of lymph node metastases was 13.6%. The median (range) number of nodes removed was 9 (1-43); there was a statistically significant correlation between the number of nodes removed and the percentage of nodal involvement (r = 0.6; P < 0.01). The rate of pN+ was significantly higher in the patients with >or= 13 than in those with < 13 nodes examined (20.8% vs 10.2%; P < 0.001). For organ-confined and locally advanced tumours there was a statistically significant difference in the pN+ rate between patients with < 13 or >or= 13 nodes examined (3.4% vs 10.5%, and 19.7% vs. 32.2%, respectively).
Conclusions: The proportion of tumours classified as pN+ increased with the number of lymph nodes examined. In RCC,> 12 lymph nodes need to be assessed for optimal staging.