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About the bladder and bladder cancer
The bladder is an expandable, hollow organ in the pelvis that stores
urine (the body’s liquid waste) before it leaves the body during
urination. The urinary tract is made up of the kidneys, ureters,
bladder, and urethra and is lined with a layer of cells called the
urothelium. This layer of cells is separated from the muscularis propria
(bladder muscles) by the lamina propria (a thin, fibrous band).
Bladder cancer begins when normal cells in the bladder lining, most
commonly urothelial cells, change and grow uncontrollably, forming a
mass called a tumor. A tumor can be benign (noncancerous) or malignant
(cancerous, meaning is can spread to other parts of the body).
Types of bladder cancer
First, the type of bladder cancer depends on the type of cell where the cancer begins:
- Urothelial carcinoma. Urothelial carcinoma accounts for about 90% of all bladder cancers and begins in the urothelium. Urothelial carcinoma is the common term for this type of bladder cancer. It was previously called transitional cell carcinoma or TCC.
- Squamous cell carcinoma. This type accounts for about 4% of all bladder cancers and starts in squamous cells, which are thin, flat cells that form part of the bladder lining.
- Adenocarcinoma. This type accounts for about 2% of all bladder cancers and begins in glandular cells.
There are other, less common cell types that can develop into bladder cancer, including sarcoma
(which begins in the fat or muscle layers of the bladder) and small
cell anaplastic cancer (a rare type of bladder cancer that is likely to
spread to other parts of the body).
In addition to its cell type, bladder cancer may be described as noninvasive, non-muscle-invasive, or muscle-invasive.
- Noninvasive. This type of bladder cancer usually does not extend through the lamina propria, while both types of invasive cancer can extend through the lamina propria. Noninvasive cancer may also be called superficial cancer, although that term is being used less often because it may incorrectly imply that this type of cancer is not serious. Noninvasive bladder cancer is less likely to spread and can often be managed with surgery to remove tumors and chemotherapy placed in the bladder (see Treatment).
- Non-muscle-invasive. Non-muscle-invasive bladder cancer typically grows only into the lamina propria. It is called invasive, but it is not the deeply invasive type that can spread to the muscle layer.
- Muscle-invasive. Muscle-invasive bladder cancer spreads into the bladder's muscularis propria and sometimes to the fatty layers or surrounding tissue outside the muscle.
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