The bladder is a hollow, expandable organ in the pelvis that stores urine until it is emptied from the body. The wall of the bladder consists of several layers: an inner layer of transitional epithelial cells, which flatten and expand as the bladder fills and empties; a middle layer of blood vessels and nerves; and an outer layer of muscle cells.
Approximately 73,000 cases of bladder cancer occur in the United States each year, mostly in males and in people older than 70. As treatment for bladder cancer has advanced, the survival rate has risen. Most people who are diagnosed with bladder cancer survive the disease.
Types of Bladder Cancer
The majority of bladder cancers — about 90 percent — begin in the cells on the surface of the inner lining of the bladder, known as transitional epithelial cells. This type of cancer is called transitional cell carcinoma (TCC), or urothelial carcinoma. Most TCCs are noninvasive, meaning the cancer stays within the bladder’s inner lining.
Many bladder cancers can be cured, but getting the best outcome requires close cooperation from a team of specialists.
In about 30 percent of cases, however, TCC tumors eventually penetrate the bladder’s lining and grow into the muscle wall. Muscle-invasive bladder cancer can also metastasize, or spread, to other parts of the body, such as the kidneys, ureters, and urethra.
Less common types of bladder cancer also can develop in the inner lining of the bladder as a result of chronic irritation and inflammation. These rare types usually grow into the muscle of the bladder over time and are characterized according to the cell type involved:
- Squamous cell carcinoma. Approximately 8 percent of bladder cancers begin in the thin, flat squamous cells that may form in the bladder after a long-term infection or irritation.
- Small cell carcinoma. Approximately 1 percent of bladder cancers start in small, nerve-like cells in the bladder called neuroendocrine cells.
- Adenocarcinoma. Approximately 1 percent of bladder cancers begin in cells that make and release mucus and other fluids in the bladder.
Several factors can increase the risk of developing bladder cancer, but one in particular stands out: People who smoke cigarettes are up to four times more likely than nonsmokers to develop the disease(1). Cigar and pipe smoking also appear to increase risk, although it is unclear by how much. Studies have shown that smoking is responsible for approximately 50 percent of bladder cancers, and researchers suspect that genetic differences may increase the risk for the disease in some smokers.
Because toxins are regularly excreted through the bladder, the risk of bladder cancer persists for many years after a person stops smoking. However, quitting can reduce the risk of developing bladder cancer, as well as the risk of recurrence.
In addition, people who work in the textile, dye, rubber, leather, paint, and printing industries are at an increased risk for bladder cancer because of likely exposure to a class of organic chemicals called aromatic amines. Some aromatic amines are known to be carcinogenic (cancer-causing).
Most other risk factors for bladder cancer are beyond personal control, however. They include the following:
- Gender: Bladder cancer is nearly three times more common in males than in females.
- Age: People are most likely to develop bladder cancer after age 70.
- History of chronic bladder problems: Studies have linked the development of bladder cancer to long-term bladder irritation and inflammation, such as that caused by infections and bladder or kidney stones.
- Use of lymphoma medicine: People who have taken the common lymphoma drug cyclophosphamide (Cytoxan®) are at higher-than-average risk for bladder cancer.
- Parasitic infection: In developing countries, 75 percent of bladder cancers are squamous cell carcinomas caused by infection with the parasitic organism Schistosoma haematobium, which is often present in untreated drinking water.
Most people with bladder cancer first notice the appearance of blood in the urine. The blood may not always be visible, however, and the symptom can go undetected.
Other symptoms of bladder cancer can include:
- a rise in the sense of urgency to urinate
- an increase in volume of urinations
- an inability to urinate despite the urge to do so
- pain when urinating
Experiencing one or more of these symptoms does not mean that you have bladder cancer, but you should be examined by a doctor to identify the cause.