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.
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 (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 outlined more in Staging .
Find out more about basic cancer terms used in this 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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