Bladder cancer is any of several types of
cancer arising from the epithelial lining (i.e., the
urothelium) of the
urinary bladder. Rarely the bladder is involved by non-epithelial cancers, such as
lymphoma or
sarcoma, but these are not ordinarily included in the colloquial term "bladder cancer." It is a disease in which abnormal cells multiply without control in the bladder.