A proposal for a novel staging system in renal pelvicaliceal urothelial carcinomas

Renal caliceal urothelial carcinomas, which have characteristic microanatomies in which the tumor directly interfaces to the renal parenchyma without intervening muscle propria, are often overstaged using the existing staging system. Relying on our analysis of 150 renal caliceal and/or pelvic urothelial carcinomas, we propose a novel staging scheme based on the extent of invasion relative to the corticomedullary junction (CMJ). Tumors were classified as category pT2 when renal parenchymal invasion was present within the CMJ and where the renal papillae and medulla were dominant. Tumors going over the CMJ were classified as pT3 with the proposed new scheme. It is very important to exclude pagetoid spread along the collecting ducts/ducts of Bellini to evaluate true invasion into the renal parenchyma. Using this revised staging scheme, 38.5% of tumors that were previously classified as pT3 were reclassified into the pT2 or pT1 groups. On multivariate Cox proportional hazard regression analysis, the extent of CMJ invasion and peripelvic fat invasion were the most significant prognostic indicators (P < .001, HR, 9.308; P = .016, HR, 2.538, respectively). In the new scheme, pT3 tumors showed a tendency to be classified toward the pT4 stage, whereas pT2 tumors were classified closer to the pT1 stage than to the pT3 (pT3 vs pT4, P = .0127; pT3 vs pT2, P < .0001). Renal parenchymal invasion beyond the CMJ has a strong prognostic impact for renal caliceal carcinomas. Using this new staging scheme, we can more precisely evaluate the level of tumor invasion.