What does the doctor do during a bladder biopsy, and how does that help him figure out whether i have cancer?

Endoscopy: The office procedure is performed by placing a telescope into the bladder and looking at the entire lining of the bladder for irregularities. Any abnormalities noted must be biopsied for a definitive diagnosis since physical changes in the lining of the bladder may mimic cancer or other benign conditions. However, the biopsy will determine if there is cancer or a benign condition present.

Bladder Biopsy: Presumably, your doctor is performing a bladder biopsy because you had blood in the urine or other symptoms that pointed towards a bladder lesion. During the procedure, a small catheter is inserted into the bladder, which allows him to look around as well as obtain tissue for the pathologist to render a proper diagnosis, the only definitive way to be sure.