Human bladder cancer: evidence for a potential irritation-induced mechanism.

Bladder cancer is one of the most common human cancers, constituting about 6% and 2% of all cancers among males and females, respectively. Over 90% of all bladder cancers are transitional cell carcinomas, with most of the remainder being squamous cell carcinomas. Smoking and occupational exposure to aromatic amines and other agents are most prominent among the risk factors identified. Inflammation of the bladder, largely by infection but also by stones or a combination of the two, may play some role in human bladder cancer development. The association between inflammation and cancer appears to be stronger for squamous cell than for transitional cell carcinoma. Stones and infection can be important factors in the development of bladder tumours in rodents, but the tumours are predominantly transitional cell rather than squamous cell carcinomas.