Bladder cancer develops from cells in the bladder growing out of control, sometimes forming a bladder tumor. These cancers sometimes spread to other areas of your body.
How Bladder Cancer Begins and Spreads
Bladder cancer usually starts in the bladder’s innermost lining called the urothelium or transitional epithelium. The cancer advances through layers of the bladder’s walls, becoming increasingly harder to treat. Sometimes this cancer grows beyond the bladder, spreading to other parts of the body. This metastasis usually begins with lymph nodes, the liver, lungs or bones.
Types of Bladder Cancer
Urothelial carcinoma is the most common type of bladder cancer. Also called transitional cell carcinoma, this cancer begins in cells lining your bladder’s interior.
Your bladder cancer includes several subtypes. The first subtype differentiates between invasive or non-invasive cancer. The second subtype differentiates between papillary or flat cancer, depending on how the tumors grow.
Invasive or Non-Invasive Bladder Cancer
Invasive bladder cancer grows into multiple layers of your bladder wall, often spreading outside of your bladder to other body parts. This spread is metastasis. Cancer metastasis makes it harder to treat.
Non-invasive bladder cancer stays in your bladder’s inner cell layer, the transitional epithelium. This means the cancer does not spread, making it easier to treat.
Papillary Tumors vs. Flat Cancers of the Bladder
Papillary tumors of the bladder grow with finger-like, slender projections from the bladder’s inner surface to its center. Papillary tumors expand without growing into the bladder’s deeper tissue layers in many cases, making these non-invasive papillary tumors.
Flat bladder carcinomas also gain a subtype of non-invasive or invasive. Non-invasive flat bladder carcinomas, also called flat carcinoma in situ, do not grow toward the bladder’s center or into deeper layers of the bladder walls.
When papillary or flat cancer grows into deeper layers of the bladder, doctors call it invasive urothelial carcinoma.
Other Bladder Cancers
Other, less common bladder cancers include:
- Squamous cell carcinoma
- Small cell carcinoma