Cancer InDepth: Kidney Cancer

Kidney cancer, also called renal cancer, refers to a malignancy that originates in the kidneys.

The kidneys are organs that filter the blood to remove liquid waste products and produce urine. Humans have two kidneys, a left and a right. The body can function with only one kidney.

Kidney cancer occurs when cells in the kidney divide without control or order. Normally, cells divide in a regulated manner. If cells keep dividing uncontrollably when new cells are not needed, a mass of tissue forms, called a growth or tumor. The term cancer refers to malignant tumors, which can invade nearby tissues and can spread to other parts of the body. A benign tumor does not invade or spread.

Different types of cancer can develop in the kidneys. The most common is renal cell carcinoma. The types of renal cell cancer are differentiated by cell type. They include clear cell, papillary, chromophobe, collecting duct, and unclassified. The other types of cancer that can develop in the kidneys are transitional cell carcinoma, which is similar to bladder cancer and treated like that disease, Wilms’ tumors (found in children), and renal sarcomas.

Who Is Affected

Each year, according to the American Cancer Society, about 51,190 Americans learn they have kidney cancer, and about 12,890 will die from the disease. More men than women develop kidney cancer. Most cases occur in people aged 50 to 70, but it can develop in children as well as adults of any age. About half of all cases are detected before the cancer has spread and half after it has invaded tissues near the kidney or in other parts of the body. The number of people who develop kidney cancer has increased during the past 20 years.

Causes and Complications

Renal cancers typically develop due to genetic changes called mutations. These mutations may be inherited, but most occur after birth. Exposure to cancer-causing substances, such as tobacco products, can trigger a genetic mutation. The chemicals in tobacco smoke are absorbed into the bloodstream. When the kidneys filter the blood, these substances can accumulate in the kidney, damage the cells, and lead to cancer. While exposure to cancer-causing substances is a risk factor for renal cell carcinoma, in most cases the cause is unknown.

Kidney cancers sometimes grow to a very large size before they are detected. Symptoms from growth of the tumor in the kidney and surrounding areas include pain in the abdomen or back, blood in the urine, fever, and weight loss. Symptoms associated with the spread of kidney cancer depend upon where the cancer is located. The condition may spread to almost all parts of the body, including the lung, bones, liver, adrenal gland, and the other kidney. Pain is common in later stages of this disease. Kidney cancer may occasionally interfere with the body's ability to filter the blood, which may require dialysis treatments in some cases. Dialysis is a procedure that filters the blood when the kidneys do not function properly.

References:

American Cancer Society website. Available at: http://www.cancer.org/docroot/home/index.asp?level=0 .

Bast R, Kufe D, Pollock R, et al, eds. Cancer Medicine. 5th ed. Hamilton, Ontario: BC Decker Inc; 2000.

Kidney Cancer Association website. Available at: http://www.kidneycancerassociation.org/ .

National Cancer Institute website. Available at: http://www.cancer.gov/ .



Last reviewed June 2007 by Miguel Antelo, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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