Malignant non-urothelial neoplasms of the urinary bladder: a review.

OBJECTIVES: Non-urothelial bladder tumors frequently present a diagnostic and therapeutic challenge. We review the peer-reviewed literature to summarize the available evidence on the etiology, diagnosis and optimal management of malignant non-urothelial bladder tumors.
METHODS: A comprehensive MEDLINE database search was performed. In addition, the proceedings of recent national and international urological and cancer society meetings were reviewed.
RESULTS: Primary non-urothelial bladder tumors are rare in Europe and North America representing less than 5% of all bladder lesions combined. A large number of risk factors have been implicated in the etiology of non-schistosomiasis-related squamous cell carcinoma, yet their exact pathomechanism remains poorly defined. Squamous cell carcinoma, adenocarcinoma, small cell carcinoma, sarcoma and carcinosarcoma/sarcomatoid tumors share an unfavorable prognosis despite aggressive surgical management that relates both to an aggressive biological behaviour as well as to an often times advanced stage at the time of diagnosis. Inflammatory pseudotumors are benign tumors of uncertain histogenesis that may mimic sarcomas. Paraganglioma, primary melanoma and lymphoma represent additional, exceedingly rare bladder tumors.
CONCLUSIONS: The systematic investigation of most non-urothelial bladder tumors is limited by the rarity of these lesions. A concerted effort of multiple institutions linked together in a national or international tumor registry will be necessary to advance our understanding of these tumors, evaluate treatment strategies and optimize patient outcome in the future.