Rare and Aggressive Disease: Urinary Bladder Leiomyosarcoma.

: Bladder leiomyosarcoma is an extremely rare non-urothelial malignancy, accounting for less than 0.1% of all bladder tumors. It presents significant diagnostic and therapeutic challenges due to its aggressive nature and the absence of standardized treatment protocols. : We report the case of a 61-year-old woman who presented with hematuria, dysuria, and suprapubic pain. Imaging revealed a large, locally invasive bladder mass, and histopathological examination following transurethral resection confirmed leiomyosarcoma. The patient underwent radical cystectomy with resection of adjacent bowel segments and urinary diversion. Histology showed a high-grade leiomyosarcoma (pT3N0) with extensive necrosis and a high mitotic index. Two months postoperatively, peritoneal dissemination was detected. Systemic chemotherapy with dacarbazine and doxorubicin initially led to the regression of metastases, but disease progression occurred within months, including lung, liver, and bone metastases. Palliative radiotherapy and second-line chemotherapy were initiated. As of now, 16 months have elapsed since surgery. : This case underscores the aggressive clinical course of bladder leiomyosarcoma despite multimodal therapy and the urgent need for individualized management strategies. Given its rarity, this case contributes to the limited literature and highlights the importance of vigilant follow-ups and further studies to establish evidence-based treatment protocols.