Bladder Cancer: Classifications

Nearly 95 percent of patients are diagnosed with a type of bladder cancer called urothelial carcinoma, also referred to as transitional cell cancer. This common type of bladder cancer is highly treatable but may recur within the bladder and requires continuing surveillance.

Because urothelial cells are also found in other parts of the urinary tract, urothelial cancer can sometimes occur in the collecting systems of the kidney and in the ureters that carry urine from the kidneys down to the bladder.

Urothelial carcinomas are divided into two subtypes, based on their pattern of growth as seen under the microscope.

  • Papillary carcinomas are slender, finger-like projections growing from the inner surface of the bladder toward the center, often without penetrating into the outer layers. These tumors are also called non-invasive papillary cancers.
  • Flat carcinomas do not grow toward the hollow center of the bladder. When a flat tumor is only in the inner layer of bladder cells, it is called a non-invasive flat carcinoma or a flat carcinoma in situ (CIS).

Less common types of bladder cancer A very small minority (fewer than 5 percent) of patients with bladder cancer have squamous cell carcinoma, adenocarcinoma, or small cell cancer.
Squamous cell carcinomas and adenocarcinomas are generally invasive, while small cell cancers of the bladder grow quickly and need to be treated aggressively.