Abnormal growth and cell division of the tissues of the bladder, the hollow organ that holds urine. Most bladder cancers are transitional cell carcinomas, which are cancers that begin within the layers of the cells lining the inner wall of the bladder. When bladder cancer is confined to the surface layer, it is called superficial bladder cancer. If superficial bladder cancer spreads through the lining of the bladder and invades the muscular wall of the bladder, it is called invasive bladder cancer. Invasive bladder cancer may spread to nearby organs.