Metastatic Urothelial Carcinoma With Sarcomatoid Subtype After Robot-Assisted Radical Cystectomy Successfully Treated With Pembrolizumab

A 76-year-old man who was diagnosed with urothelial carcinoma (UC) in the bladder diverticulum was referred to our institution. The patient was diagnosed with muscle-invasive bladder cancer, which was confirmed by magnetic resonance imaging that showed tumor invasion into the fatty tissue surrounding the diverticulum. After two cycles of neoadjuvant gemcitabine and cisplatin, he underwent robot-assisted radical cystectomy (RARC) with pelvic lymph node dissection followed by intracorporeal ileal conduit. The histopathologic diagnosis of the bladder tumor was UC with squamous differentiation and sarcomatoid subtype and ypT3bN0M0 without positive surgical margins. The patient refused any adjuvant therapy. Six months after RARC, the patient visited our institution with a complaint of suddenly occurring generalized pain. Because