One way to discuss bladder cancer is to describe what kind of cells it starts from. The bladder is made up of many layers of cells. Bladder cancer can affect any one or all of these cells. These are the three types of cells most commonly affected:
Urothelial cells (also called transitional cells). These cells make up the tissue that line the inside of the bladder called the urothelium. Cancer in this area is called urothelial carcinoma or transitional cell carcinoma (TCC). This type is the most common bladder cancer.
Squamous cells. These look like cells from the skin. They lie under the transitional cells.
Cells that make up glands. This type of bladder cancer is called adenocarcinoma. It is very rare. Only 1 to 2 percent of people with bladder cancer have this type.
Another way to talk about bladder cancer is by how deeply it invades the wall of the bladder. The two main classifications for bladder cancer are superficial and invasive:
Superficial bladder cancer. This is cancer that affects only the lining of the bladder. After treatment, superficial bladder cancer may come back, usually as another superficial cancer. Many transitional cell cancers are superficial.
Invasive bladder cancer. This cancer affects deeper layers of the bladder, which may include the outer muscular wall. Invasive bladder cancer may spread to nearby organs, such as the kidneys, the prostate gland (in men), and the uterus and vagina (in women). It may also spread to the lymph nodes. Lymph nodes are small, pea-sized storage units for special cells that fight infections. Clusters of lymph nodes are located in the groin, abdomen, chest, underarms, and neck. Almost all squamous cell bladder cancers and adenocarcinomas are invasive.
Transitional cell carcinomas (also known as urothelial carcinomas) may also be described as being either papillary or flat:
Papillary tumors. These look like small mushrooms and grow into the open part of the bladder. They rarely invade other parts of the bladder. Some types of papillary tumors tend to come back. However, they can be removed fairly easily with minimal damage to the bladder itself. These tumors may be superficial or invasive. Invasive bladder tumors penetrate the inner bladder wall and can spread to other parts of the body.
Flat tumors. These do not grow into the open part of the bladder. They may be either superficial or invasive.