Topographic distribution of first landing sites of lymphatic metastases from patients with renal cancer.

INTRODUCTION AND OBJECTIVE: Adjuvant studies with checkpoint inhibitors have attracted new interest in accurate pathological lymph node (LN) staging in renal cell carcinoma. Sentinel lymph node (SN) studies in cN0 patients revealed the pattern of lymphatic radiotracer drainage from renal tumors. The aim of this study was to describe the location of single- or oligometastatic LN and analyze if the topography of these first landing sites matches the drainage pattern observed in SN studies of renal tumors. MATERIALS AND METHODS: We collected data from 8 referral centers from 1990 to 2018 of all patients with pT1-4 cN0 or cN1 M0 renal cell carcinoma with pathologically confirmed single- or oligometastases in locoregional LN. The location of LN metastases, number, size of metastatic LN, and survival were analyzed using descriptive statistics with SPSS version 22 (IBM, Chicago, IL). RESULTS: From 3,794 patients with histologically confirmed pN1, a total of 76 patients (2%) with single- or oligometastatic pN1 were identified, of whom 24 (31.6%) and 52 (68.4%) were cN0 and cN1, respectively. On the left side, LN metastases were predominantly located in the para-aortal (48.0%; 95% confidence interval [CI] 29.22-63.12%) and hilar (31.42%; 95% CI 17.4-49.4%) area. On the right side, metastases located in retrocaval (26.82%; 95% CI 14.7-43.2%), hilar (26.82%; 95% CI 14.7-43.2%), interaortocaval (26.82%; 95% CI 14.7-43.2%), and paracaval (17.07%; 95% CI 7.6-32.6%) LNs. These landing sites exactly matched the lymphatic drainage pattern of intratumorally injected radiotracer reported in SN studies for both sides. CONCLUSIONS: Single- or oligometastatic LNs in renal cancer are mainly located in the hilar, retro-, para, and interaortocaval region on the right side and para-aortal region on the left side. These first landing sites match the drainage pattern reported in SN trials.