How the Bladder Works

The bladder is a hollow organ in the lower part of the abdomen. It is shaped like a small balloon and has a muscular wall that allows it to get larger or smaller.  The bladder stores urine until it is passed out of the body. Urine is the liquid waste that is made by the kidneys as they clean the blood.  Urine passes from the two kidneys into the bladder through two tubes called ureters. When the bladder is emptied during urination, the urine goes from the bladder to the outside of the body through a tube called the urethra.

What is Bladder Cancer?

Cancer is a disease where cells change and grow out of control. In most cases of bladder cancer, cancer begins in the cells that line the inside wall of the bladder. These changing cells can behave differently. They may form a lump of tissue (tumor) or spread to other parts of the body. They may change quickly or slowly.

The wall of the bladder is lined with cells called transitional cells and squamous cells.

More than 90% of bladder cancers begin in the transitional cells. This type of cancer is called transitional cell carcinoma.

About 8% of bladder cancer begins in the squamous cells. This type of cancer is called squamous cell carcinoma.

Cancer that is only in cells in the lining of the bladder is called superficial bladder cancer or carcinoma in situ.

Cancer that begins as a superficial tumor may grow through the lining and into the muscular wall of the bladder, becoming invasive cancer. Invasive cancer may extend through the bladder wall. It may grow into a nearby organ such as the uterus or vagina (in women) or the prostate gland (in men). It also may invade the wall of the abdomen. When bladder cancer spreads outside the bladder, cancer cells are often found in nearby lymph nodes. If the cancer has reached these nodes, cancer cells may have spread to other lymph nodes or other organs, such as the lungs, liver, brain or bones. This is called metastatic bladder cancer.