What Is Bladder Cancer?

Bladder cancer occurs when abnormal cells grow in the bladder. The bladder is a hollow organ in the lower part of the abdomen that collects liquid waste (urine) and stores it until the urine exits the body. According to the American Cancer Society (ACS), bladder cancer was diagnosed in about 70,530 people and caused approximately 14,680 deaths in the United States in 2010.

The Urinary System

Your bladder is a triangle-shaped, hollow organ with muscular walls in the lower part of the abdomen (pelvis). It is held in place by ligaments (bands of strong tissue) that are attached to other organs and the pelvic bones. The bladder's walls relax and expand to store urine; they contract and flatten to empty urine through the urethra. The typical healthy adult bladder can store up to 2 cups of urine for 2 to 5 hours.

Your body’s two kidneys make urine. Two tubes (ureters) carry the urine to the bladder. The bladder empties the urine through another tube called the urethra. In women, the urethra is a very short tube that ends just in front of the vagina. In men, the urethra is longer; it goes through the prostate gland and ends at the tip of the penis.

The wall of the bladder has several layers:

• Urothelium or transitional epithelium - A layer of transitional cells (cells that change their shape depending on whether the tissue is being stretched) that line the inside wall of the kidney, ureter, bladder, and urethra.
• Lamina propria - A thin layer of connective tissue under the urothelium.
• Muscularis propria - A layer of tissue, or muscle, outside the lamina propria.
• Layer of fatty connective tissue - Separates the bladder from other nearby organs.
  

How Bladder Cancer Starts

Bladder cancer develops when cells that are part of the bladder grow out of control and can become cancer. Most bladder cancer forms on the walls of the organ.

Cells from a bladder tumor can break away and enter the veins leaving the bladder. They can then travel through the blood vessels to other parts of the body where they form tumors. Bladder cancer cells can also spread to other organs through lymphatic vessels, which carry lymph (a clear fluid that contains tissue waste products and immune system cells) to lymph nodes (small, bean-shaped collections of immune system cells that help fight infections.) When cancer spreads to other organs, this process is called metastasis.

Types of Bladder Cancer

Any bladder cancer not limited to the urothelium is classified as invasive.

There are several cell types of bladder cancer:

• Transitional cell carcinoma or urothelial carcinoma - The cancer begins in the transitional cells (cells that change their shape depending on whether the tissue is being stretched) lining the bladder. Transitional cell carcinoma is the most common kind of bladder cancer, accounting for about 90 percent of cases.
• Squamous cell carcinoma - The cancer begins in squamous cells (thin, flat cells that form the surface of the skin, the lining of the body’s hollow organs, and the passages of the respiratory [breathing] and digestive tracts.) About 4 percent of bladder cancers are squamous cell carcinomas.
• Adenocarcinoma - The cancer begins in the cells of glandular structures (cells that produce secretions that help other parts of the body work). Adenocarcinomas account for only about 1 or 2 percent of bladder cancers.

There are also several different types of transitional cell or urothelial tumors:

• Noninvasive urothelial tumors - The cancer is only in the innermost layer of the bladder, the urothelium, and has not spread to deeper layers.
• Invasive urothelial tumors - The cancer has spread from the urothelium to the deeper layers of the bladder wall.
• Superficial urothelial tumors - This category includes noninvasive cancers and some invasive cancers that have not spread deeply into the bladder wall. The cancer is only in the layers of urothelial cells closest to the inside of the bladder or it has spread to the thin layer of connective tissue (lamina propria) just beneath the urothelial cells. Once a cancer has invaded the bladder's main muscle layer, it is not considered superficial.
• Papillary urothelial tumors - Papillary tumors have slender finger-like projections that grow into the bladder’s hollow center. Papillary urothelial tumors can be invasive or noninvasive.
• Flat urothelial tumors - Noninvasive flat urothelial carcinomas (also known as flat carcinoma in situ) involve only the layer of cells closest to the inside or hollow part of the bladder. Flat invasive urothelial carcinomas invade the deeper layers (away from the hollow part), particularly the muscle layer.

Key Statistics

Bladder cancer is the fourth most frequent cancer diagnosed in men and the ninth most frequent cancer diagnosed in women. A man’s chance of developing bladder cancer some time in his life is about 1 in 27; this rate is 1 in 85 for a woman.

The average age of onset is 60 to 70. Whites are twice as likely to develop bladder cancer as blacks. Hispanics are even less likely to get bladder cancer than blacks.

More than 500,000 people living in the United States have survived bladder cancer.

This content has been reviewed and approved by Myo Thant, MD.