Cancer starts when cells in the body begin to grow out of control. Cells in nearly any part of the body can become cancer, and can spread to other areas of the body. To learn more about how cancers start and spread, see What Is Cancer?
Bladder cancer starts in the bladder. To understand bladder cancer, it helps to know about the normal bladder and what it does.
The normal bladder
The bladder is a hollow organ that stores urine. Urine is made in the kidneys and flows into the bladder through thin tubes called ureters. Urine leaves the bladder through another tube called the urethra. In women the urethra is very short. In men it is longer and passes through the prostate gland to the tip of the penis.
The wall of the bladder has several layers. The innermost layer of the bladder is called the urothelium. Most bladder cancers start there. Over time, they can grow into or through the other layers of the bladder, and then can spread outside the bladder. As the cancer grows through the layers it becomes more advanced and harder to treat.
Types of bladder cancer
There are different types of bladder cancer. The type you have can affect your treatment options because different types need different treatments.
Transitional cell carcinoma (TCC)
This is by far the most common type of bladder cancer. It starts in the inner layer of the bladder – the urothelium – so it is also called urothelial carcinoma.
This group has subtypes:
- Papillary cancers grow like tiny fingers from the inner bladder lining toward its hollow center.
- Flat cancers do not grow toward the center.
These tumors are also named based on whether they have grown into the bladder wall:
- Non-invasive cancers are still in the inner layer of cells (the urothelium) but have not grown into the deeper layers.
- Invasive cancers have grown into the deeper layers of the bladder. These cancers are more likely to spread and are harder to treat.
Other cancers that start in the bladder
Squamous cell carcinoma: This type is much less common and is usually invasive.
Adenocarcinoma: This type is also much less common, and almost all are invasive.
Small-cell carcinoma: A very small number of bladder cancers are of this type. These cancers often grow quickly.
The rest of this document deals only with transitional cell (urothelial) cancers of the bladder.
Last Revised: 01/21/2016