Clinical significance of squamous differentiation in upper tract urothelial carcinoma treated with radical nephroureterectomy.

Abstract

451 Background: Upper tract urothelial carcinoma (UTUC) involving the renal pelvis/ureter is histologically similar to bladder cancer in morphological diversity. Although squamous differentiation (SD) is the most common variant in UTUC, the clinical significance of SD in UC has yet to be comprehensively elucidated given the rarity of the disease compared to bladder cancer. To assess the impact of SD on the prognosis of patients with UTUC undergoing radical nephroureterectomy (RNU). Methods: Among the 244 consecutive patients who underwent RNU at our single institution from May 2005 to October 2019, only patients who had histologically confirmed pure UC or UC with SD (UCSD) were included. SD required the presence of intercellular bridges or keratinization for diagnosis. Metastasis-free survival (MFS) and overall survival (OS) rates were retrospectively evaluated using Kaplan–Meier analysis and Cox regression analysis. Results: We identified 197 (87.9%) and 27 (12.1%) patients with pure UC and UCSD, respectively. No significant differences in age, sex, concomitant carcinoma in situ and tumour grade were observed between the groups. UCSD was significantly associated with an advanced tumour stage and a higher rate of lymphovascular invasion. With a median follow-up time of 58 months, the pure UC and UCSD groups had a 5-year MFS rate of 65.2% and 40.9% ( p=0.005) and a 5-year OS rate of 74.4% and 49.0% ( p=0.002), respectively. Multivariate analyses revealed that the presence of SD was significantly associated with MFS [hazard ratio (HR), 1.88; p=0.027] and OS (HR, 1.70; p=0.048). Conclusions: The patients with UCSD are at high risk for disease metastasis and short-term survival. SD in UC could be an independent predictor of poor prognosis after RNU for UTUC.