Understanding the Different Types and Forms of Bladder Cancer
Reviewed by: HU Medical Review Board | Last review date: September 2017. | Last updated: February 2023
A person develops bladder cancer when some of the cells inside the bladder start to change the way they grow and divide.1 Healthy cells grow and divide in a regular and consistent way, with older cells dying off as new ones grow and take the place of the old cells. Cancer cells grow in an uncontrolled way. New cancer cells keep developing, but the old cancer cells do not die off as they should. The cancer cells can start to crowd out the healthy cells.
What is a bladder tumor?
When cancer cells start growing in the bladder, they can form a group of cells called a bladder tumor. A bladder tumor is sometimes called a bladder mass. Bladder tumors made up of cancer cells are called malignant tumors, and these cancer cells can spread to other parts of the body outside of the bladder.
It's not always cancer
A growth of cells in the bladder can be called a bladder tumor, a bladder lesion, a bladder mass, or a bladder polyp. A growth on the bladder is not always bladder cancer. For example, a tumor that is benign (not cancerous) can grow bigger, but will not spread to other parts of the body. Bladder polyps are growths in the bladder than can be benign or malignant. If your healthcare provider detects an abnormal growth of cells in your bladder, then more testing will help to find out if it is cancerous or not.
Are there different types of bladder cancer?
There are several different types of bladder cancers.2 However, one type of bladder cancer—called urothelial carcinoma—is by far the most common in the United States. Other types of bladder cancer include:
- Squamous cell carcinoma
- Small cell carcinoma
What is a urothelial carcinoma?
Around 90% of people who are diagnosed with bladder cancer in the United States have the type called urothelial carcinoma.2,3 It is called “urothelial” because the cancer cells start out by developing in the lining of the bladder walls, in a layer of cells called the urothelium. Another name for this type of bladder cancer is transitional cell carcinoma.
Figure 1. Layers of the bladder wall
If you are diagnosed with urothelial carcinoma, your healthcare providers will perform tests to find out more about the cancer cells. Before beginning treatment for bladder cancer, it is important to know what type of tumor it is, and how the cancer cells are growing in the bladder.
Invasive or non-invasive bladder cancer
Bladder cancer can be invasive or non-invasive. If it is non-invasive, then all the cancer cells are still located in the thin layer of cells in the lining of the bladder wall (the urothelium) and have not grown deeper into the bladder. If it is invasive, then the cancer cells have grown deeper into the bladder wall. Bladder cancer that is invasive is more likely to spread into the bladder muscle and on to other areas of the body.
The shape of a bladder tumor can be either papillary or flat. Both papillary and flat tumors can be invasive or non-invasive, depending upon how the cancer cells have grown.
Papillary or flat tumors
Papillary tumors grow out from the inner lining toward the hollow center of the bladder, in slim finger-shaped growths. These are often non-invasive, because they grow outward from the bladder lining rather than inward deeper into the bladder walls. One type of slow growing, non-invasive papillary bladder cancer is called papillary urothelial neoplasm of low malignant potential (PUNLMP).
Flat bladder tumors (also called sessile) do not grow into the hollow part of bladder, but grows in a flat shape instead. If a flat tumor has not grown outside of the urothelium layer of cells, then it is non-invasive. If it has grown deeper into the bladder wall, then it is called invasive.
Figure 2. Different types of bladder tumors
What are less common forms of bladder cancer?
Squamous cell carcinoma of the bladder is a type of bladder cancer that is very rare in the United States.1-3 The cancer cells look different under a microscope than the type of cancer cells involved in urothelial bladder cancer. Squamous cell carcinomas in the bladder tend to be the invasive type of cancer. This type affects less than 5% of people diagnosed with bladder cancer in the United States.
An even more rare type of bladder cancer is called adenocarcinoma of the bladder, which affects around 1%-2% of people diagnosed with bladder cancer in the United States.1-3 It also tends to be invasive.
Bladder sarcomas are the rarest type, which occur in less than 1% of people with bladder cancer in the United States.1-3 Unlike most other types of bladder cancer, which start in the bladder lining, the cancer cells in sarcomas start growing in the muscle of the bladder.