What Is Bladder Cancer

Types of bladder cancer
Urothelial carcinoma (transitional cell carcinoma)
Urothelial carcinoma, also known as transitional cell carcinoma (TCC), is by far the most common type of bladder cancer. In fact, if you have bladder cancer it's almost certain to be a urothelial carcinoma. These cancers start in the urothelial cells that line the inside of the bladder.

Urothelial cells also line other parts of the urinary tract, such as the part of the kidney that connects to the ureter (called the renal pelvis), the ureters, and the urethra. People with bladder cancer sometimes have tumors in these places, too, so all of the urinary tract needs to be checked for tumors.

Other types of bladder cancer
Other types of cancer can start in the bladder, but these are all much less common than urothelial (transitional cell) cancer.

Squamous cell carcinoma
In the US, only about 1% to 2% of bladder cancers are squamous cell carcinomas. Seen with a microscope, the cells look much like the flat cells that are found on the surface of the skin. Nearly all squamous cell carcinomas of the bladder are invasive.

Adenocarcinoma
Only about 1% of bladder cancers are adenocarcinomas. These cancer cells have a lot in common with gland-forming cells of colon cancers . Nearly all adenocarcinomas of the bladder are invasive.

Small cell carcinoma
Less than 1% of bladder cancers are small-cell carcinomas. They start in nerve-like cells called neuroendocrine cells. These cancers often grow quickly and usually need to be treated with chemotherapy like that used for small cell carcinoma of the lung.

Sarcoma
Sarcomas start in the muscle cells of the bladder, but they are very rare. More information can be found in Soft Tissue Sarcoma and Rhabdomyosarcoma.

These less common types of bladder cancer (other than sarcoma) are treated a lot like TCCs, especially early-stage tumors, but if chemotherapy is needed, different drugs might be used.

Start and spread of bladder cancer
The wall of the bladder has many several layers. Each layer is made up of different kinds of cells (see Bladder Cancer Stages for details on the different layers).

Most bladder cancers start in the innermost lining of the bladder, which is called the urothelium or transitional epithelium. As the cancer grows into or through the other layers in the bladder wall, it has a higher stage, becomes more advanced, and can be harder to treat.

Over time, the cancer might grow outside the bladder and into nearby structures. It might spread to nearby lymph nodes, or to other parts of the body. (When bladder cancer spreads, it tends to go to distant lymph nodes, the bones, the lungs, or the liver.)

Invasive vs. non-invasive bladder cancer
Bladder cancers are often described based on how far they have spread into the wall of the bladder:

Non-invasive cancers are only in the inner layer of cells (the transitional epithelium). They have not grown into the deeper layers.
Invasive cancers have grown into deeper layers of the