Common Types of Bladder Cancer

There are several common types and subtypes of bladder cancer, with each one possessing its own characteristics in regard to cells it starts in, the way it looks and how it spreads. Urothelial carcinomas, squamous cell carcinoma and adenocarcinoma account for the majority of all bladder cancers.

Urothelial Carcinoma (also called Transitional Cell Carcinoma)

• Sometimes still known as transitional cell carcinomas, urothelial carcinomas are the most common variety, accounting for between 90 and 97 percent of all diagnosed bladder cancers. These cancers begin in the innermost layer of the bladder, the transitional cells. Transitional cells, also called the urothelial layer of cells, shrink when the bladder is emptied and stretch when the bladder is full.

  Urothelial carcinomas can be categorized by invasiveness. If the cancer remains in the transitional cells, it is noninvasive. A cancer spreading to the layer below the transitional cells is invasive, and cancer spreading into deeper layers, such as the muscular or fatty layers, is considered deeply invasive. Urothelial carcinomas are divided into papillary and flat subtypes.

Papillary Urothelial Carcinomas

• Papillary urothelial carcinomas, also called papillary tumors, are a subtype of urothelial cancer that project into the bladder's central hollow area. These projections, known as polyps, can be finger-like, flower-shaped or cactus-shaped. The growths protruding into the hollow center of the bladder are considered noninvasive and generally have good treatment outcomes, butsome papillary urothelial carcinomas can be invasive if they grow into deeper bladder tissue layers.

Flat Urothelial Carcinomas

• Flat urothelial carcinomas, also known as flat carcinomas, are another subtype of urothelial carcinomas. These carcinomas look like flat lesions on the cell layer closest to the inside of the bladder. Flat carcinomas remain on the lining of the bladder and do not grow into the hollow area of the bladder. Flat carcinomas come in two varieties. The noninvasive variety can also be called carcinoma in situ (does not spread) The invasive variety, also called invasive transitional cell carcinoma, can spread to other layers of cells, even extending into the muscle tissue.

Squamous Cell Carcinomas

• Squamous cells are flat thin cells, and they may form after prolonged irritation or infection. When viewed through a microscope, these cells resemble the flat cells of the surface of the skin. Squamous cell carcinomas are almost always invasive, spreading beyond their immediate area.

Adenocarcinomas

• Adenocarcinomas arise in the glandular cells of the bladder. These cancers account for roughly 1 percent of all bladder cancers diagnosed. Bladder adenocarcinomas are almost always invasive cancers, which means that they are likely to spread out of the immediate layer of cells. These cancer cells have traits in common with the gland-forming cells found in colon cancers.

Rare Bladder Cancers

• Though uncommon, other, more rare types should be mentioned. Small-cell carcinomas account for less than 1 percent of all bladder cancers. This cancer type is rare, and it is treated much the same way as small-cell carcinomas of the lung. Cancers starting in the bladder's muscle cells, called sarcomas or soft-tissue cancers, are another rare type of bladder cancer.