What Is Bladder Cancer?
The bladder is a hollow organ in the lower abdomen (pelvis). It collects and stores urine produced by the kidneys.
- The bladder is connected to the kidneys by a tube from each kidney called a ureter.
- When the bladder reaches its capacity of urine, the bladder wall contracts, although adults have voluntary control over the timing of this contraction. At the same time, a urinary control muscle (sphincter) in the urethra relaxes. The urine is then expelled from the bladder.
- The urine flows through a narrow tube called the urethra and leaves the body. This process is called urination, or micturition.
Cancer occurs when normal cells undergo a degenerative, dangerous, or what is called a malignant change or transformation causing them to grow abnormally and multiply without normal controls. A mass of cancerous cells is called a malignant tumor or cancer. The cancerous cells are capable of spreading to other areas of the body through the process of metastasis. A cancer can become destructive locally to the tissues adjacent to where it arises. Cancer cells can also metastasize. Metastasis means that cells spread through the tissue fluid's circulation called the lymphatic system or through the bloodstream where they can then stop off in other tissues or organs where they may grow as metastases or metastatic deposits and can become destructive in these new locations. The term cancer is further described by the tissue in which it has arisen. For example: bladder cancer is a different disease than lung cancer. If a bladder cancer cell metastasizes -- that is, spreads to the lungs through the bloodstream it is still called, and is treated as metastatic bladder cancer, not as lung cancer.
Cells which transform in a less dangerous fashion may still multiply and form masses or tumors. These are called benign tumors. They do not metastasize.
Of the different types of cells that form the bladder, the cells lining the inside of the bladder wall are those most likely to develop cancer. Any of three different cell types can become cancerous. The resulting cancers are named after the cell types.
- Urothelial carcinoma (transitional cell carcinoma): This is by far the most common type of bladder cancer in the United States. The so-called transitional cells are normal cells that form the innermost lining of the bladder wall, the urothelium. In transitional cell carcinoma, these normal lining cells undergo changes that lead to the uncontrolled cell growth characteristic of cancer.
- Squamous cell carcinoma: These cancers are comprised of cells that typically form as a result of bladder inflammation or irritation that has taken place for many months or years. These cells grow in flat masses of interconnected cells.
- Adenocarcinoma: These cancers form from cells that make up glands. Glands are specialized structures that produce and release fluids such as mucus.
- In the United States, urothelial carcinomas account for more than 90% of all bladder cancers. Squamous cell carcinomas make up 3%-8%, and adenocarcinomas make up 1%-2%.
- Only transitional cells normally line the rest of the urinary tract. The kidney's internal collecting system, the ureters (narrow tubes that carry urine from the kidneys to the bladder), the bladder, and the urethra are lined with these cells. Thus, individuals with transitional cell cancers of the bladder are at risk for transitional cell cancers of the kidneys/ureter (upper urinary tract).
Last Reviewed 11/21/2017
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