Bladder cancer forms in the tissue layers of the bladder, which is a hollow, expandable and muscular organ that stores urine for excretion. Bladder cancer accounts for about 90 percent of cancers of the urinary collection system, which includes the renal pelvis, ureters and urethra.
Bladder cancers are described based on how the cells look under a microscope. Each type of bladder cancer – there are three main kinds – respond differently to varying treatments. Typically, bladder cancer originates in the bladder lining, which is made up of transitional epithelial cells. It begins when normal cells in the bladder grow uncontrollably and form masses, called tumors. In addition two other types of bladder cancer are worth mentioning, including adenocarcinoma which is a cancer that originates in the cells that manufacture and release mucus and the squamous cell carcinoma which is a cancer that prospers in the thin, flat cells of the bladder.
According to the National Cancer Institute, bladder cancer is the fourth most common type of cancer for men and the eighth most common in women. The biggest risk factors are smoking and exposure to carcinogens in the workplace. Studies now also show that type-2 diabetes patients who have been taking Actos (pioglitazone) for one year or longer have a higher risk factor for bladder cancer. The institute estimates that there will be 73,510 new bladder cancer cases in the United States in 2012. There are several types of bladder cancer.
Transitional cell (also called urothelial cell) carcinoma is the most common kind of bladder cancer – it accounts for 90 percent of bladder cancer cases. It is characterized by a lump or tumor that forms in or on the bladder.
Within the transitional cell type of bladder cancer, there are subcategories that describe where the tumor is growing and how much it has spread.
Superficial – This type of bladder cancer is contained mostly on the transitional cell layers and has not spread beyond the bladder lining and connective tissue. It is also called carcinoma in situ. The recurrence rate for this cancer is known to be between 60 and 80 percent.
Invasive - As undetected superficial bladder cancer spreads, it invades the deeper tissue layers of the organ. It can also move into the nearby muscle tissue.
Metastatic - When invasive bladder cancer spreads to nearby organs, it is said to be metastatic. It can enter the lymphatic system and travel to the liver, lungs and bones.
This type of bladder cancer usually occurs after long-term infections, such as ongoing urinary tract infections, chronic kidney infections or chronic bladder irritations, such as bladder stones. Continuing infections or irrigations can cause transitional cells into squamous cells, which are at a greater risk of turning into to cancer.
Squamous cell bladder cancer is also known to affect those living in countries where parasites are common.
A rare form of bladder cancer, adenocarcinoma accounts for just 1 to 3 percent of all bladder cancers. It is known as an aggressive and dangerous cancer.