Bladder cancer can occur at any age, but it is most common in people older than 50 years of age. The average age at the time of diagnosis is in the 60s. However, it clearly appears to be a disease of aging, with people in their 80s and 90s developing bladder cancer as well.

Firstly, the bladder is a hollow organ in the lower abdomen (pelvis). It collects and stores urine produced by the kidneys. Cancer occurs when normal cells undergo a transformation whereby they grow and multiply without normal controls.

As the cells multiply, they form an area of abnormal cells. Medical professionals call this a tumor. As more and more cells are produced, the tumor increases in size. Tumors overwhelm surrounding tissues by invading their space and taking the oxygen and nutrients they need to survive and function.

Of all types of cancer, bladder cancer has an unusually high propensity for recurring after treatment. Bladder cancer has a recurrence rate of 50%-80%. The recurring cancer is usually, but not always, of the same type as the first (primary) cancer. It may be in the bladder or in another part of the urinary tract (kidneys or ureters).

Bladder cancer is most common in industrialized countries. It is the fifth most common type of cancer in the United States the fourth most common in men and the ninth in women.

Important to mention, Tumors are cancerous only if they are malignant. This means that, because of their uncontrolled growth, they encroach on and invade neighboring tissues. Malignant tumors may also travel to remote organs via the bloodstream or the lymphatic system.

This process of invading and spreading to other organs is called metastasis. Bladder cancers are most likely to spread to neighboring organs and lymph nodes prior to spreading through the blood stream to the lungs, liver, bones, or other organs.

Bladder cancers are classified (staged) by how deeply they invade into the bladder wall, which has several layers. Many physicians subdivide bladder cancer into superficial and invasive disease. Superficial bladder cancer is limited to the innermost linings of the bladder (known as the mucosa and lamina propria). Invasive bladder cancer has at least penetrated the muscular layer of the bladder wall.

Nearly all adenocarcinomas and squamous cell carcinomas are invasive. Thus, by the time these cancers are detected, they have usually already invaded the bladder wall.

Many urothelial cell carcinomas are not invasive. This means that they go no deeper than the superficial layer (mucosa) of the bladder.

Of the different types of cells that form the bladder, the cells lining the inside of the bladder wall are most likely to develop cancer. Any of three different cell types can become cancerous. The resulting cancers are named after the cell types.

In the United States, urothelial carcinomas account for more than 90% of all bladder cancers. Squamous cell carcinomas make up 3%-8%, and adenocarcinomas make up 1%-2%.

Urothelial carcinoma (transitional cell carcinoma) is by far the most common type of bladder cancer in the United States. The so-called transitional cells are normal cells that form the innermost lining of the bladder wall.

In transitional cell carcinoma, these normal lining cells undergo changes that lead to the uncontrolled cell growth characteristic of cancer.

Squamous cell carcinoma originate from the thin, flat cells that typically form as a result of bladder inflammation or irritation that has taken place for many months or years.

Adenocarcinoma cancers form from cells that make up glands. Glands are specialized structures that produce and release fluids such as mucus.

These three types of cancer can develop anywhere in the urinary tract. If abnormal cells are found anywhere in the urinary tract, a search for other areas of abnormal cells is warranted. For example, if cancerous cells are found in the bladder, an evaluation of the kidneys and ureters is essential.

Furthermore, a tumor grade is based on the degree of abnormality observed in a microscopic evaluation of the tumor. Cells from a high-grade cancer have more changes in form and have a greater degree of abnormality when viewed microscopically than do cells from a low-grade tumor.

This information is provided by the pathologist, a physician trained in the science of tissue diagnosis. Low-grade tumors are less aggressive, whereas high-grade tumors are more dangerous and have a propensity to become invasive.

Papillary tumors are urothelial carcinomas that grow narrow, finger-like projections. Benign (noncancerous) papillary tumors (papillomas) grow projections out into the hollow part of the bladder. These can be easily removed, but they sometimes grow back.

These tumors vary greatly in their potential to come back (recur). Some types rarely recur after treatment; other types are very likely to do so. Papillary tumors also vary greatly in their potential to be malignant (invasive). A small percentage (15%) do invade the bladder wall. Some invasive papillary tumors grow projections both into the bladder wall and into the hollow part of the bladder.

In addition, bladder cancer can develop in the form of a flat, red (erythematous) patch on the mucosal surface. This is called carcinoma-in-situ (CIS).

Although these tumors are superficial, they are high-grade and have a high risk for becoming invasive.

Interesting fact about bladder cancer is that, white men and women, develop bladder cancers twice as often as other ethnic groups. In the United States, African Americans and Hispanics have similar rates of this cancer. Rates are lowest in Asians.

Lastly, because of its high recurrence rate and the need for lifelong surveillance, bladder cancer is the most expensive cancer to treat on a per patient basis.