Bladder cancer is the most common cancer of the urinary tract. Bladder cancer occurs most commonly between the ages of 50 and 70. It is twice as common in men as in women. Cancer-causing agents (carcinogens) in the urine may lead to the development of bladder cancer.

The bladder is a hollow organ in the lower abdomen (pelvis). It collects and stores urine, liquid waste produced by the kidneys. Urine passes from each kidney into the bladder through a tube called ureter and leaves the bladder through the urethra. The wall of the bladder has several layers. A layer of urothelial cells (also called transitional cells) lines the inside of the the kidney, ureter, bladder, and urethra. This layer is called the urothelium or transitional epithelium. Beneath the urothelium, there is a thin zone of connective tissue called the lamina propria. The next deeper layer is a wider zone of muscle tissue called muscularis propria. Beyond this muscle, another zone of fatty connective tissue separates the bladder from other nearby organs. As the cancer penetrates through these layers into the wall of the bladder, it becomes harder to treat.