Introduction to Bladder Cancer

The urinary bladder is a hollow, balloon-like organ located in the pelvis that collects and stores urine until it is ready to be excreted from the body. Urine is produced in the kidneys and is transported to the bladder through two tube-like structures called ureters. Pressure from the accumulation of urine in the urinary bladder forces the wall of the bladder to contract producing the urge to urinate. The urine is then excreted from the bladder via the urethra (a thin tube that carries urine from the bladder to the outside of the body).

The wall of the bladder is composed of several different layers that are important in understanding the development, progression, and treatment of bladder cancer. When viewed under a microscope, a cross-section of the bladder wall reveals the following layers of cells:

• Epithelium - The epithelium is a layer of cells that lines the inside of the bladder wall and is also known as the urothelium or transitional epithelium. The vast majority of bladder cancers originate in the transitional epithelium.

• Lamina propria - This is the layer of connective tissue and blood vessels located immediately beneath the transitional epithelium.

• Muscularis propria - This is the deep layer of muscle cells that form the wall of the bladder.

• Perivesicle soft tissue - This is the outermost layer of the bladder wall that consists of fat, fibrous connective tissue, and blood vessels. Bladder cancer that has spread to the perivesicle soft tissue is considered as having spread outside of the bladder.