A case series: Four cases of urothelial carcinoma with sarcomatoid differentiation

Urothelial carcinoma with sarcomatoid differentiation (UCSD) is a rare and highly aggressive variant of urothelial carcinoma associated with poor prognosis. UCSD originating in the upper urinary tract is extremely uncommon, and its variable morphological presentation, along with the lack of established treatment guidelines, often poses diagnostic and therapeutic challenges. We herein report four cases of upper tract UCSD treated with radical nephroureterectomy. All tumors exhibited varying proportions (40%-90%) of sarcomatoid components with diverse histological patterns. Postoperatively, patients received adjuvant chemotherapy. Through this case report and review of the relevant literature, we aim to enhance the understanding of this rare entity and contribute to the discussion on optimal treatment strategies for upper tract UCSD.