Nearly all cancers of the bladder start in the layer of cells which form the lining (urothelium) of the bladder. These are called transitional cell or urothelial cell cancers. They come in a very wide range of forms and can behave in very different ways. For example, they may occur as a small, wart-like growth on the inside of the bladder, which can be removed in a simple operation and may never come back. Sometimes they can form a large tumour which grows into the muscle wall of the bladder and needs major surgery.

Other, rarer, types of bladder cancer are squamous cell cancer and adenocarcinoma. Squamous cell cancer starts from one of the types of cell in the bladder lining. Adenocarcinoma starts from glandular cells which produce mucus.

Some bladder cancers form warty outgrowths or mushroom-like growths on the inside lining of the bladder. These are called papillary cancers. They have a short stem attached to the lining of the bladder. Sometimes they go on to spread into the wall of the bladder.

If a bladder cancer only affects the inner lining of the bladder, it is known as a superficial cancer. If it has spread into the muscle wall of the bladder, it is called an invasive cancer.