Extranodal extension in regional lymph nodes is associated with outcome in patients with renal cell carcinoma

The 2002 American Joint Committee on Cancer pN classification for renal cell carcinoma is based on the number of positive regional lymph nodes. We examined the associations of pathological features of lymph node metastases with patient outcome to improve the prognostic accuracy of the current classification.

We studied the records of 2,076 patients treated with radical nephrectomy for unilateral, sporadic pM0 renal cell carcinoma between 1970 and 2000. There were 34 patients with metastasis in a single regional lymph node (pN1) and 35 with metastases in more than 1 lymph node (pN2). Pathological features of lymph node metastases, including the number and percent of positive lymph nodes, total number of lymph nodes removed, grade, necrosis, extranodal extension, and largest dimension and surface area of metastases were determined by 2 urological pathologists (HHD and JCC).

There was no statistically significant association between the pN classification and death from renal cell carcinoma (pN2 vs pN1 RR 1.05, 95% CI 0.62 to 1.79, p = 0.846). However, patients with extranodal extension were twice as likely to die of renal cell carcinoma than patients in whom metastases did not extend outside of the lymph node capsule (RR 2.02, 95% CI 1.18 to 3.45, p = 0.010). The 5-year cancer specific survival rate was 18% and 35% in patients with and without extranodal extension, respectively.

We believe that a pN classification based on the presence or absence of lymph node metastases with a notation regarding the presence or absence of extranodal extension represents a significant improvement in the prognostic accuracy of the current pN classification.