Learn The BasicsThe most common type of bladder cancer is urothelial carcinoma, also known as transitional cell carcinoma.
There are other, less common types of bladder cancer, including squamous cell carcinoma, adenocarcinoma, small cell carcinoma and sarcoma.
Urothelial carcinoma
Urothelial carcinoma is the most common type of bladder cancer and is especially common among older adults.
In this type, the cancer starts in the urothelial cells lining the inside of the bladder.
The urothelial cells line the renal pelvis, which connects to the ureters, the ducts that carry urine from the kidneys to the bladder. These cells can also be found in the ureters themselves and the urethra, the duct that carries urine from the bladder to the outside. Therefore, all these areas may be affected by bladder cancer.
When the bladder is empty, the urothelial cells are bunched up together, and they stretch out in a single layer when the bladder fills with urine and they come into contact with waste products in the urine. Chemicals in the urine, like the ones found in tobacco, coming into contact with these cells can cause them to become cancerous.
Urothelial carcinoma can either be non-muscle invasive, in which the cancer has not invaded the deeper layers of the bladder, or muscle invasive, in which the cancer has grown into the deeper muscle layer of the bladder wall and/or beyond.
Non-muscle invasive urothelial carcinoma tends to be less aggressive and is usually treated with localized therapy like transurethral resection.
Muscle-invasive urothelial carcinoma makes up around 25% of all bladder cancers and is far more likely to spread than the non-muscle invasive type.
Squamous cell carcinoma
Squamous cell carcinoma makes up only 3 to 5% of all bladder cancer cases in the U.S. However, it is more common in some parts of the world, like Africa and Asia, where it may be caused by a parasitic infection called bilharzia.
In this type of bladder cancer, cancer cells look like the flat cells that are found on the surface of the skin, under the microscope. These types of cells may form in the bladder after long-term infection or irritation.
This type of bladder cancer is usually invasive.
Adenocarcinoma
Adenocarcinoma is even rarer, making up only 1 to 2% of all bladder cancer cases. It is also usually invasive.
This type of bladder cancer develops in glandular cells, which produce fluids like mucus.
Small cell carcinoma
Small cell carcinoma is rarer still, making up less than 1% of bladder cancer cases.
This type of bladder cancer starts in nerve-like cells called neuroendocrine cells, which are cells that receive signals from the nervous system and release hormones as a response.
This type of bladder cancer often grows quickly and is usually treated with chemotherapy.
Sarcoma
Sarcomas are cancers that start in connective tissues in the body. In case of bladder cancer, they may start in the muscle cells of the bladder..
However, this type of bladder cancer is very rare.