A mass in the bladder may be bladder cancer, a blood clot in the bladder, or a benign tumor such as a papilloma of the bladder. In all of these cases, further cystoscopy is required to observe the lesion under cystoscopy and obtain a biopsy of the lesion for laboratory testing to reach a final diagnosis. If the mass in the bladder has surface bleeding or destruction of the surrounding mucosa, it may be a bladder cancer. The majority of these appear to be hydrophobic or seaweed-like and require local biopsy for final diagnosis. Papilloma mainly presents as a papillary-like protrusion of the bladder with an unsmooth surface that may be associated with bleeding but is not associated with significant pain. It is a benign lesion but needs to be surgically removed otherwise there is a risk of later transformation to papillary carcinoma. Local mucosal bleeding due to inflammatory changes in the bladder can also form a blood clot, which can also appear as a mass on imaging without colored blood flow signals. Cystoscopy can be performed to clarify whether the clot is a blood clot or even to expel the clot through the cystoscope.