Impact of micropapillary histological variant on survival after radical nephroureterectomy for upper tract urothelial carcinoma

To assess the impact of micropapillary histological variant on oncological outcome after radical nephroureterectomy (RNU) for upper urinary tract urothelial carcinomas (UTUCs). A French multicenter retrospective study was performed on patients who underwent RNU between 1995 and 2010. Pathological reports were reviewed to identify patients with pure urothelial carcinomas (PUC) and those with micropapillary histological variant (MPC). Uni- and multivariate Cox regression analyses were performed to identify factors predictive of survival. Overall, 519 patients were included and divided into two groups: 480 PUC and 39 MPC. Median follow-up were 28 and 19 months, respectively (p = 0.63). There was no difference between the two groups for gender, age and tumor location (pelvicalyceal or ureteral). MPC was associated with high-stage and high-grade UTUC (p < 0.001 and 0.04). No difference was observed between the two groups for 5-year cancer-specific survival (76.1 vs. 88.2 %; p = 0.54). The 5-year metastasis-free survival was significantly lower in the MPC group (48.9 vs. 73.8 %; p = 0.037). In multivariate analysis, pT stage, lymphovascular invasion, margin status and adjuvant chemotherapy administration were independent predictors of specific survival (p = 0.002; 0.001; 0.02; 0.01), contrary to histological variant (p = 0.94). Micropapillary histological variant was associated with advanced UTUC and reduced metastasis-free survival after RNU. It should be considered as an aggressive tumor and thus be stated in any pathological report after radical surgery.