Where does bladder cancer start?

Bladder cancer starts in the bladder, a hollow, balloon-shaped organ in the lower part of the abdomen that stores urine. It occurs when cells in the bladder start to grow without control.

Almost all bladder cancers begin in the urothelial cells that line the inside of the bladder. This type is called urothelial carcinoma, also known as transitional cell carcinoma. These cells are also called transitional cells because they can stretch when the bladder is full of urine and shrink when it is empty.

Other, rarer types of bladder cancer include squamous cell carcinoma, adenocarcinoma, and small cell carcinoma of the bladder. Your healthcare team can explain more about the type of bladder cancer in your situation.