Remarkable Response to Immune Checkpoint Inhibition After Early Aggressive Recurrence Following Robot‐Assisted Radical Cystectomy for Bladder Squamous Cell Carcinoma: A Case Report

ABSTRACT Introduction Squamous cell carcinoma is a rare bladder cancer subtype with poor prognosis in advanced stages. Currently, there is no established systemic therapy, including immune checkpoint inhibitors, for this subtype. Case Presentation A 49‐year‐old man with pure bladder squamous cell carcinoma arising from a diverticulum with pelvic lymph node involvement underwent neoadjuvant gemcitabine plus cisplatin followed by robot‐assisted radical cystectomy. Six months later, pulmonary metastases developed, and platinum rechallenge led to rapid progression with pleural dissemination. Pembrolizumab produced a complete response despite programmed cell death ligand‐1 negativity, microsatellite stability, and low tumor mutational burden. Isolated hilar lymph node progression during treatment was managed with radiotherapy, achieving temporary local control. The patient survived 41 months from diagnosis and 30 months after metastasis. Conclusion Despite early and aggressive metastatic recurrence after robot‐assisted radical cystectomy, the patient showed a remarkable and durable response to pembrolizumab.