Several types of cancer can start in the bladder
Urothelial carcinoma, also known as transitional cell carcinoma (TCC), is by far the most common type of bladder cancer. In fact, if you are told you have bladder cancer it is 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. Patients with bladder cancer sometimes have other tumors in these places, so the entire urinary tract needs to be checked for tumors.
Bladder cancers are often described based on how far they have invaded into the wall of the bladder:
A bladder cancer can also be described as superficial or nonmuscle invasive. These terms include both noninvasive tumors as well as any invasive tumors that have not grown into the main muscle layer of the bladder.
Bladder cancers are also divided into 2 subtypes, papillary and flat, based on how they grow (see image above).
If either a papillary or flat tumor grows into deeper layers of the bladder, it is called an invasive urothelial (or transitional cell) carcinoma.