The bladder is a small organ in the body that stores the urine. According to the American Cancer Society (ACS), the bladder is composed of several layers. Bladder cancer usually starts in the lining, or urothelium, and grows through the layers, into the walls of the bladder. There are several different types of bladder cancer, including some that are very rare. The type of bladder cancer is classified by what the cancerous cells look like when viewed under a microscope.
Transitional Cell Carcinoma
Transitional cell carcinoma, the most common bladder cancer, accounts for almost 90 percent of bladder cancers. It is also referred to as urothelial carcinoma, as it begins in the urothelial cells. An interesting fact about transitional cell carcinoma, reported by Cancer Research UK, is that when the bladder is empty, the cancer cells are grouped together, yet when the bladder is full, they stretch apart as the bladder wall stretches. Under the heading of transitional cell carcinoma, bladder cancer can be typed as invasive, meaning it will grow into the deeper layers of the bladder, or superficial, which indicates that the cancer cells are on the lining of the bladder and can easily be removed. Transitional carcinoma can be caused by toxic chemicals that may be in the urine.
Squamous Cell Carcinoma
Cancer Research UK reports that squamous cell carcinoma accounts for only 2 percent of bladder cancers. The squamous cells are smooth, flat cells that make up the moist lining of the bladder, and the ACS reports that squamous cell bladder cancer is often invasive, spreading further into other bladder tissues and, possibly, other organs. This type of cancer can be caused by chronic bladder irritation or infections.
Adenocarcinoma
While squamous cell carcinoma forms in the cells that compose the lining of the bladder that is covered with mucous, the National Cancer Institute reports that adenocarcinoma begins in the cells that produce that mucous. Adenocarcinoma accounts for between 1 and 2 percent of bladder cancer diagnoses and can also be caused by chronic infection and irritation of the bladder. The ACS states that adenocarcinoma is usually invasive, spreading to other parts of the bladder, and possibly neighboring organs.
Soft Tissue Carcinoma and Small Cell Bladder Cancer
Soft tissue carcinoma is a very rare type of bladder cancer, and it begins in the deeper tissues of the bladder, such as muscle tissue, and not in the lining of the bladder as most of the other bladder cancers do.
Small cell bladder cancer is also extremely rare. It can begin in any area of the bladder and is very invasive. According to Cancer Research UK, small cell bladder cancer is treated through surgical removal of the bladder.
