Definition of Bladder cancer:

Bladder cancer is a cancerous tumor in the bladder -- the organ that holds urine.

Causes, incidence, and risk factors:

In the United States, bladder cancers usually start from the cells lining the bladder (transitional cells).

These tumors may be classified based on the way they grow:

• Papillary tumors have a wart-like appearance and are attached to a stalk.
• Nonpapillary tumors are much less common. However, they are more invasive and have a worse outcome.

As with most other cancers, the exact cause of bladder cancer is uncertain. However, several factors may contribute to its development:

• Cigarette smoking. Smoking increases the risk of developing bladder cancer nearly fivefold. As many as 50% of all bladder cancers in men and 30% in women may be caused by cigarette smoke. People who quit smoking have a gradual decline in risk.
• Chemical exposure at work. About one in four cases of bladder cancer is caused by exposure to cancer-causing chemicals (carcinogens) on the job. Dye workers, rubber workers, aluminum workers, leather workers, truck drivers, and pesticide applicators are at the highest risk. Arylamines are the chemicals most responsible. However, arylamines have been reduced or eliminated in many workplaces.
• Radiation and chemotherapy. Women who received radiation therapy for the treatment of cervical cancer have an increased risk of developing transitional cell bladder cancer. Some people who have received the chemotherapy drug cyclophosphamide (Cytoxan) are also at increased risk.
• Bladder infection. A long-term (chronic) bladder infection or irritation may lead to the development of squamous cell bladder cancer. Bladder infections do not increase the risk of transitional cell cancers.
• Parasite infection. In third world countries, infection with the schistosomiasis parasite has been linked to the development of bladder cancer.

The association between artificial sweeteners and bladder cancer has been studied and is weak or nonexistent.

Bladder cancers are classified, or staged, based on their aggressiveness and how much they differ from the surrounding bladder tissue. There are several different ways to stage tumors. Recently, the TNM (Tumor, Nodes, Metastasis) staging system has become common. This staging system categorizes tumors using the following scale:

• Stage 0 -- Non-invasive tumors that are only in the bladder lining
• Stage I -- Tumor goes through the bladder lining, but does not reach the muscle layer of the bladder
• Stage II -- Tumor goes into the muscle layer of the bladder
• Stage III -- Tumor goes past the muscle layer into tissue surrounding the bladder
• Stage IV -- Tumor has spread to neighboring lymph nodes or to distant sites (metastatic disease)

Bladder cancer spreads by extending into the nearby organs, including the:

• Prostate
• Rectum
• Ureters
• Uterus
• Vagina

It can also spread to lymph nodes in the pelvis, or to other parts of the body, such as:

• Bones
• Liver
• Lungs