Risk factors in clonal development from superficial to invasive bladder cancer.

Bladder cancer has classically been associated with exogenous risk factors, and a large literature has identified risk factors associated with the genesis of transitional cell carcinoma. Only recently have efforts been made to identify host factors and to evaluate possible changes in tumour presentation and biology, including grade and stage, in association with these risk factors. The available literature appears to demonstrate alterations in tumour biology associated with environmental carcinogens. Various studies have suggested a consistent upgrading of bladder cancer stage and grade as a result of cigarette smoking and high risk occupational exposures. It is important, however, that all factors associated with increased risk for bladder cancer be more extensively evaluated in assessing the validity of this concept.