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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. This function makes the bladder an important part of the urinary tract, which is also made up of the kidneys, ureters, and urethra.
The bladder, like other parts of the urinary tract, is lined with a layer of cells called the urothelium. This layer of cells is separated from the muscularis propria (bladder wall muscles) by a thin, fibrous band known as the lamina propria.
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 cancerous or benign. A cancerous tumor is malignant, meaning it can spread to other parts of the body. A benign tumor means the tumor will not spread.
Types of bladder cancer
The type of bladder cancer depends on how it looks under the microscope.
Urothelial carcinoma. Urothelial carcinoma accounts for about 90% of all bladder cancers and begins in the urothelial cells lining the bladder. Urothelial carcinoma is the common term for this type of bladder cancer. It was previously called transitional cell carcinoma or TCC.
Squamous cell carcinoma. Squamous cells develop in the bladder lining in response to irritation and inflammation. Over time these cells may become cancerous. Squamous cell carcinoma accounts for about 4% of all bladder cancers.
Adenocarcinoma. This type accounts for about 2% of all bladder cancers and begins in glandular cells.
There are other less common types of bladder cancer, including sarcoma, which begins in the fat or muscle layers of the bladder, and small cell anaplastic cancer, which is 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 (superficial), 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 the tumor and chemotherapy placed in the bladder (see the Treatment Options section).
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 grows into the bladder's wall muscle (muscularis propria) and sometimes to the fatty layers or surrounding tissue outside the bladder.
It is important to note that both noninvasive and non-muscle-invasive bladder cancers have the possibility of spreading into the bladder muscle or to other parts of the body. Additionally, all cell types of bladder cancer can metastasize (spread) beyond the bladder. If the tumor has spread into the surrounding organs, such as the uterus and vagina in women, the prostate in men, and/or nearby muscles, it is called locally advanced disease.
Bladder cancer also often spreads to the lymph nodes in the pelvis. If it has spread into the liver, bones, lungs, lymph nodes outside the pelvis, or other parts of the body, the cancer is called metastatic disease. This will be described in more detail in the Stages section.
Looking for More of an Overview?
If you would like additional introductory information, explore the following item on Cancer.Net:
- ASCO Answers Fact Sheet: Read a one-page fact sheet (available in PDF) that offers an easy-to-print introduction for this type of cancer.
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- Medical Illustrations
- Risk Factors
- Symptoms and Signs
- Stages and Grades
- Treatment Options
- About Clinical Trials
- Latest Research
- Coping with Side Effects
- After Treatment
- Questions to Ask the Doctor
- Additional Resources
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