The wall of the bladder is lined with cells called transitional cells and squamous cells. More than 90 percent of bladder cancers begin in the transitional cells. This type of bladder cancer is called transitional cell carcinoma. About 8 percent of bladder cancer patients have squamous cell carcinomas.
Cancer only in cells in the lining of the bladder is called superficial bladder cancer. This type of bladder cancer often comes back after treatment, but it does not tend to progress. If the tumor recurs, the disease often recurs as another superficial cancer in the bladder. Cancer that begins as a superficial tumor may grow through the lining and into the muscular wall of the bladder. This is known as invasive cancer. Invasive cancer may extend through the bladder wall. It may grow into a nearby organ such as the uterus or vagina in women or the prostate gland in men. It also may spread to other parts of the body.
When bladder cancer spreads outside the bladder, cancer cells are often found in nearby lymph nodes. If the cancer has reached these nodes, cancer cells may have spread to other lymph nodes or other organs, such as the lungs, liver or bones.
When cancer spreads or metastasizes from its original place to another part of the body, the new tumor has the same kind of abnormal cells and the same name as the primary tumor. For example, if bladder cancer spreads to the lungs, the cancer cells in the lungs are actually bladder cancer cells. The disease is metastatic bladder cancer, not lung cancer. It is treated as bladder cancer, not as lung cancer. Doctors sometimes call the new tumor “distant” disease.
Fortunately, the majority of bladder cancers do not grow rapidly and can be treated without major surgery. Thus, most patients with bladder cancer are not at risk of developing a cancer that will spread and become life threatening. Early detection is vital; it allows the prompt treatment that gives patients the best chance for a favorable outlook.