There are three basic types of bladder cancer, which are named for the type of cells that become cancerous (malignant).

More than 90 percent of bladder cancers are classified as urothelial carcinoma, which is also known as transitional cell carcinoma (TCC). Urothelial carcinoma has several subtypes,  which are named according to the shape of the cancer cells (flat or with papillary projections) and whether the cells are invasive or noninvasive. These subtypes include:

• Noninvasive urothelial tumors. The cancer affects only the urothelium (the innermost layer of a patient’s bladder wall) and has not spread to other layers of the bladder wall.
  
  
• Invasive urothelial tumors. The cancer has spread to other layers of the bladder wall.
  
  
• Superficial urothelial tumors. This category includes noninvasive bladder cancers, as well as some invasive cancers that have not spread into the deeper layers of the bladder wall.
  
  
• Papillary urothelial tumors.  These tumors have slender projections that resemble fingers and may be further subdivided into other types.
  
  
• Flat urothelial tumors. Flat urothelial tumors can invade either close to the hollow center of the bladder or the bladder wall's deeper layers.

In addition to urothelial tumors, the other two types of bladder cancer include:

• Squamous cell carcinoma. This type of bladder cancer, from another type of lining cell, is usually invasive, and far less common than urothelial carcinoma. Squamous cell carcinoma accounts for approximately 4 percent of bladder cancers, according to the ACS.
  
  
• Adenocarcinoma. This type of bladder cancer, from the glands in the bladder, is also much less common than urothelial carcinoma, and tends to invade other organs. The ACS maintains that just 1 to 2 percent of bladder cancers are adenocarcinomas.

Though other types of bladder cancer do exist, they tend to be very rare. Individuals can also develop a number of benign bladder tumors, which are typically removed by surgery and do not pose any health risks.