Bladder cancer is the uncontrolled growth of cells, usually originating in the bladder lining. The bladder is an organ located in the pelvic cavity that stores and discharges urine. Urine is produced by the kidneys, carried to the bladder by hollow tubes called ureters, and discharged from the bladder through a tube called the urethra.
The uncontrolled growth of these abnormal bladder cells eventually form tumors. A tumor is a mass or lump of tissue made of these uncontrolled, abnormal cells. Tumors can be benign or malignant. Benign tumors are not cancerous, and cells from benign tumors do not spread to other parts of the body. In most cases, benign tumors do not come back after they are removed. Benign tumors are rarely a threat to life. Malignant tumors are cancerous. They are generally more serious and can and invade and damage nearby tissues and organs.
The wall of the bladder is lined with cells called transitional cells and squamous cells. More than 90% of bladder cancers begin in the transitional cells. The same type of cells occurs in the kidneys, ureters, and urethra, where malignant tumors may also be found.
Some bladder cancers remain confined to the bladder lining (called carcinoma in situ). But other cancers are invasive, growing into or through the bladder wall, and eventually into nearby lymph nodes and adjacent organs. The cancer may metastasize (spread) over time to other organs, including the vagina and uterus in women, the prostate in men, and the lungs, liver, or bones.
Bladder cancer accounts for approximately 90% of cancers of the urinary tract, including renal pelvis, ureters, bladder, and urethra.
Bladder cancer is the sixth most common cancer in the United States. According to the American Cancer Society, about 53,200 Americans are diagnosed with bladder cancer each year and 12,200 die annually of the disease. The estimated new cases and deaths from bladder cancer in the U.S. in 2007 are 67,160 and 13,750, respectively.
According to the National Cancer Institute (NCI), the highest incidence of bladder cancer occurs in industrialized countries such as the U.S., Canada, and France. Incidence is lowest in Asia and South America, where it is about 70% lower than in the United States.
Smoking is the greatest single risk factor for bladder cancer.
Treating bladder cancer that has metastasized (spread) can be difficult, but if the bladder cancer is detected early, before it has metastasized, the chances of a successful treatment with minimal side effects is likely.
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If bladder cancer is diagnosed, the doctor needs to know the stage, or extent, of the disease to plan the best treatment. Staging is a careful attempt to find out whether the cancer has invaded the bladder wall, whether the disease has spread, and if so, to what parts of the body.
The doctor may determine the stage of bladder cancer at the time of diagnosis, or may need to give the patient more tests, such as CT scan, magnetic resonance imaging (MRI), intravenous pyelogram, bone scan, or chest x-ray. Sometimes staging is not complete until the patient has surgery.
The stage refers to the physical location of the tumor within the bladder or, more specifically, the tumor's depth of penetration. In general, tumor stage is confined to one of two categories: (1) superficial, surface tumors, or (2) invasive, deep-spreading tumors. Superficial tumors affect only the bladder lining. They grow up and out from the lining tissue and extend into the bladder's hollow cavity. Invasive tumors grow down into the deeper layers of bladder tissue, and they may involve surrounding muscle, fat, and/or nearby organs. Invasive tumors are more dangerous than superficial tumors, since they are more likely to metastasize.
This determination requires a diagnostic procedure using a cystoscopic examination that includes a biopsy and examination under general anesthesia to assess the size and movement of the tumors, the degree of hardening of the bladder wall, and the presence of malignancy (spreading) to nearby organs. Clinical staging often underestimates the extent of tumor.
The American Joint Committee on Cancer (AJCC) has designated staging by TNM classification to define bladder cancer. TNM designates the tumor, N designates regional lymph node involvement, and M designates metastasis (spreading).
The stages are then further divided into stage groupings, consisting of; Stage 0, where the cancer cells are found only on the surface of the inner lining of the bladder (generally called superficial cancer or carcinoma in situ; Stage I, where the cancer cells are found deep in the inner lining of the bladder but may not have not spread to the muscle of the bladder; Stage II, where the cancer cells have spread to the muscle of the bladder; Stage III, where the cancer cells have spread through the muscular wall of the bladder to the layer of tissue surrounding the bladder. The cancer cells may have spread to the prostate (in men) or to the uterus or vagina (in women); and Stage IV, where the cancer extends to the wall of the abdomen or to the wall of the pelvis. The cancer cells may have spread to lymph nodes and other parts of the body far away from the bladder, such as the lungs.