Background The aim of this study was to improve understanding of the characteristics of micropapillary urothelial carcinoma (MPUC) in the renal pelvis and ureter, and to compare oncological outcomes between MPUC and non-MPUC.

Methods From September 1994 to October 2010, 418 patients underwent nephroureterectomy with bladder excision due to presumed urothelial carcinoma. Pathological review of all specimens was done by one uropathologist. Perioperative data from these patients were reviewed retrospectively. Patients were divided into MPUC and non-MPUC groups. Oncological outcomes were compared between the two groups via progression-free survival (PFS) and cancer-specific survival (CSS) rates.

Results A total of 386 patients were included in the study. Of these, seven patients (1.81%) had MPUC. The median follow-up duration was 39.0 months (IQR range 21.1–70.6). All MPUC patients were men and had lymphovascular invasion, and six patients (85.7%) had grade III and T3 disease. On univariable analysis, MPUC showed significantly worse prognosis with regard to disease progression (p<0.001). In the subgroup analysis confined to T3 or T4 disease, MPUC showed worse prognosis than non-MPUC in terms of PFS and CSS, respectively (p<0.05). In the multivariable model, MPUC still remained a statistically significant independent predictor for PFS (HR (95% CI)=3.85 (1.59–9.32), p=0.003). MPUC was associated with poorer CSS than non-MPUC (p<0.001).

Conclusions We have observed that upper tract MPUC is associated with poor oncological outcomes in terms of PFS and CSS. MPUC was an independent prognostic factor for PFS in multivariable analysis.