What is Bladder Cancer?

Bladder cancer is a malignant overgrowth of the cells of the bladder. Most commonly, the growth occurs in cells that are in the urothelium. The lining of most hollow spaces in the body is made of  epithelial cells. The lining of the inside of your cheek, for instance, is an epithelial cell lining. Also, the lining of your stomach, bowels, gallbladder, and—you guessed it—the bladder is made of epithelial cells. Each organ has its own subset of epithelial cells. In the bladder, the lining cells are called transitional epithelial cells. The cancer that grows from these cells is then called transitional cell cancer; 90% to 95% of all bladder cancers are of this type.

If the cancer grows from a different type of cell in the bladder, it is given a different name. Other types of uncommon cancers in the bladder include squamous cell carcinoma and adenocarcinoma (carcinoma is another word for cancer). A very rare type of bladder cancer that occurs only in children is called rhabdomyosarcoma. It is also possible that cancer in the bladder did not begin there but spread to the bladder from somewhere else. The bladder is an uncommon place for other tumors to “seed” (or  metastasize), but it does occasionally occur. Although metastases are uncommon, tumors can occasionally grow directly into the bladder from an adjacent organ, such as the prostate, colon, rectum, or cervix.