Solitary fibrous tumors (SFTs) can involve the urinary bladder. They may be discovered incidentally or present with hematuria and urinary obstruction. This low power view shows a spindle cell proliferation in a dense collagenous stroma. Given their rarity, SFTs are often mistaken for sarcomatoid carcinoma or sarcomas. Immunoreactivity for CD34 and bcl-2 and lack of staining with cytokeratins, EMA, and smooth muscle markers is diagnostic.