The main type of bladder cancer is transitional cell carcinoma that begins in the cells lining the bladder and upper urinary tract. These cells are able to change shape depending on whether the bladder is full or empty and may be stretched without breaking apart. Typical tumors are delicate frond-like polyps which rise off the bladder surface.  As they grow, these tumors are susceptible to local injury, and often result in painless bleeding into the urine.

Cystoscopic view of typical papillary (frond-like) bladder tumor

While there are other types of bladder cancer, they are quite rare.  Squamous cell carcinoma is rare, may be seen with chronic irritation or infections from urinary stones or urinary catheters.  Adenocarcinoma, also uncommon, may begin in glandular (secretory) cells that may produce mucus; these cells are in the remnant of tissue (urachus) leading from the top of the bladder that was part of the umbilical cord in the fetus.

Cancer that is confined to the lining of the bladder is called superficial bladder cancer. Cancer that begins in the transitional cells may spread through the lining of the bladder and invade the muscle wall of the bladder. This is called invasive bladder cancer. If the cancer cells spread to nearby organs and lymph nodes, then it is called metastatic bladder cancer.