How is Bladder Cancer Classified?
Reviewed by: HU Medical Review Board | Last review date: September 2017. | Last updated: March 2021
What is urothelial carcinoma?
The most common form of bladder cancer is called urothelial carcinoma, which is sometimes called transitional cell carcinoma.1,2,3 In the United States, around 90% of people who are diagnosed with bladder cancer have urothelial carcinoma.
Cancers are diagnosed based on where the cancer cells first begin to form in the body. In people with urothelial carcinoma, the cancer cells start growing in a part of the bladder called the urothelium. The bladder is a hollow, flexible organ that is mostly muscle, but the urothelium is a thin layer of cells that lines the inside of the bladder. When cancer cells keep growing, they can gather together and form a mass of cells called a tumor.
There are several different types of urothelial carcinoma. The kind a person has depends on whether or not the bladder cancer cells have spread into other parts of the bladder or to other parts of the body outside of the bladder. If you are diagnosed with bladder cancer, then your healthcare providers will carry out tests to find out more about the cancer cells. In order to help develop a treatment plan for you, they will check to see how many tumors there are, what size the tumors are, and where the tumors are located.
Three types of urothelial carcinoma (bladder cancer) are:
- Non-muscle-invasive bladder cancer
- Muscle-invasive bladder cancer
- Metastatic bladder cancer (has spread to other parts of the body)
What is non-muscle-invasive bladder cancer?
Non-muscle-invasive bladder cancer is diagnosed if the bladder cancer has not spread anywhere beyond the bladder lining (the urothelium) or the lamina propria.2,4 The lamina propria is another very thin layer of cells that lies between the urothelium and the muscles in the bladder wall.
Treatment for non-muscle-invasive bladder cancer is effective for many people. It often involves a special type of surgery called transurethral resection, in which the surgeon removes the tumor from the lining of the bladder. This may be followed with other treatments to help keep the bladder cancer cells from recurring (growing back again).
What is muscle-invasive bladder cancer?
Muscle-invasive bladder cancer is diagnosed if the bladder cancer cells have spread out of the urothelium and have grown into the walls of the bladder, which is made up of muscle.2,4 This type of bladder cancer usually requires more extensive treatment, because muscle-invasive bladder cancer tends to be more likely to spread outside of the bladder to other parts of the body.
Treatment for muscle-invasive bladder cancer depends upon many factors and can be different for each person. Some people may need to have part or all of their bladder removed through surgery. Surgery is often combined with other treatments, such as radiation or chemotherapy, to treat the cancer and potentially help reduce the chance that the cancer will recur or spread to other parts of the body.
What is metastatic bladder cancer?
Metastatic bladder cancer is diagnosed if the bladder cancer cells have spread outside of the bladder and are growing in other parts of the body.2,4 If you have been diagnosed with metastatic bladder cancer, your healthcare providers will talk with you in detail about the advantages and disadvantages of the different treatment options available.
What is the difference between low-grade and high-grade bladder cancer?
During the process of diagnosis, healthcare providers also classify bladder cancer as low-grade or high-grade.4
Low-grade bladder cancer is less likely to grow into the muscles of the bladder wall and less likely to metastasize, or spread to other parts of the body. It is more common in people who have non-muscle-invasive bladder cancer.
High-grade bladder cancer is more likely to grow into the muscles in the wall of the bladder. It is also more likely to spread outside of the bladder into other parts of the body. This type is more common in people with muscle-invasive bladder cancer and metastatic bladder cancer.