The bladder is the organ in the body where urine is stored before it is expelled through urination. There are several different kinds of bladder cancer:
* Transitional cell carcinomas (cancer that begins in cells that normally make up the inner lining of the bladder) are the most common.
* Squamous cell carcinoma is cancer that begins in thin, flat cells.
* Adenocarcinoma is cancer that begins in cells that make and release mucus and other fluids.
The cells that cause squamous cell carcinoma and adenocarcinoma grow in the inner lining of the bladder and are caused by chronic irritation and inflammation.
Cancer that is in cells in the lining of the bladder is called superficial bladder cancer. Your doctor might call it carcinoma in situ. This kind of bladder cancer comes back many times, even after treatment. When the cancer returns, it is usually as another superficial cancer in the bladder.
Cancer that begins as a superficial tumor can grow through the lining and into the wall of the bladder. When this happens, it is known as "invasive" cancer. Invasive cancer can grow through the bladder wall. It can also grow into nearby organs like the uterus or vagina in women or into the prostate gland in men. This type of invasive cancer can also attack the walls of the abdomen.
When cancer spreads from one organ to another organ in the body, the new tumor will have the same kinds of cells as the original tumor. That is, if cancer cells that originated in the bladder invade the lungs, the cancer cells in the lungs are actually bladder cells. The tumor in the lung will be treated as though it were bladder cancer rather than as lung cancer. Sometimes doctors call new tumors "distant" disease.