Staging and terminology of superficial urinary bladder tumors.

Ta and T1 transitional cell urinary bladder tumors are prone to recurrence in a large percentage of cases, but they uncommonly progress to invasive tumors. On the other hand, Tis bladder tumors progress to invasive tumors in a majority of cases. Even though all of these tumors are found in the superficial layers of the bladder wall, their natural histories are significantly different. In addition, new terminology has been developed for these lesions.