About the bladder, renal pelvis, and ureter
The bladder is a hollow organ in the pelvis that stores urine before it leaves the body during urination. This function makes the bladder an important part of the urinary tract. The urinary tract is also made up of the kidneys, ureters, and urethra. The renal pelvis is a funnel-like part of the kidney that collects urine and sends it into the ureter. The ureter is a tube that runs from each kidney into the bladder. The urethra is the tube that carries urine out of the body. The prostate gland is also part of the urinary tract.
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 bladder wall muscles, called the muscularis propria, by a thin, fibrous band called the lamina propria.
Bladder cancer begins when healthy cells in the bladder lining—most commonly urothelial cells—change and grow out of control, forming a mass called a tumor. Urothelial cells also line the renal pelvis and ureters and urethra. Cancer that develops in the renal pelvis and ureters is also considered a type of urothelial cancer and is often called upper tract urothelial cancer. In most cases, it is treated in much the same way as bladder cancer and is described in this guide. A tumor can be cancerous or benign. A cancerous tumor is malignant, meaning it can grow and spread to other parts of the body. A benign tumor means the tumor can grow but will not spread. Benign bladder tumors are very rare.
Types of bladder cancer
The type of bladder cancer depends on how the tumor’s cells look under the microscope. The 3 main types of bladder cancer are:
- Urothelial carcinoma. Urothelial carcinoma (or UCC) accounts for about 90% of all bladder cancers. It also accounts for 10% to 15% of kidney cancers diagnosed in adults. It begins in the urothelial cells that line the urinary tract. Urothelial carcinoma used to be 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 develops from glandular cells.
There are other, less common types of bladder cancer, including micropapillary, plasmacytoid, sarcomatoid carcinoma of the bladder, and small cell bladder cancer, among others. Sarcomas of the bladder often begin in the fat or muscle layers of the bladder. Small cell bladder cancer is a rare type of bladder cancer that is likely to spread to other parts of the body.
Other ways of describing bladder cancer
In addition to its cell type, bladder cancer may be described as noninvasive, non-muscle-invasive, or muscle-invasive.
- Noninvasive. Noninvasive bladder cancer includes noninvasive papillary carcinoma and carcinoma in situ (CIS). Noninvasive papillary carcinoma is a growth found on a small section of tissue that is easily removed. This is called stage Ta. CIS is cancer that is found only on or near the surface of the bladder, which is called stage Tis. See Stages and Grades for more information.
- Non-muscle-invasive. Non-muscle-invasive bladder cancer typically has only grown into the lamina propria and not into muscle, also called stage I. Non-muscle-invasive cancer may also be called superficial cancer, although this term is being used less often because it may incorrectly suggest that the cancer is not serious.
- Muscle-invasive. Muscle-invasive bladder cancer has grown into the muscle of the bladder wall and sometimes into the fatty layers or surrounding tissues or organs outside the bladder.
It is important to note that non-muscle-invasive bladder cancer has the potential of spreading into the bladder muscle or to other parts of the body. Additionally, all cell types of bladder cancer can spread beyond the bladder to other areas of the body through a process known as metastasis.
If a bladder tumor has spread into the surrounding organs, such as the uterus, vagina, prostate gland, 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 is described in more detail in Stages and Grades.