From: cancerbackup.org.uk

" Transitional cell carcinoma is the commonest type of bladder cancer.

Doctors describe cancers according to where in the body they occur and what type of cells they have started from. Most cancers of the bladder start from the lining tissue inside the bladder. The lining of the bladder and other parts of the urinary system are made up of transitional cells. These cells aren't normally found anywhere else in the body.

Although transitional cell carcinoma most commonly affects the bladder, occasionally it may start in the ureter, the tube joining the kidney to the bladder, or the part of the kidney that is closest to the ureter. "