Kidney cancer is begins in one or both of the kidneys, the organs that filter out waste and extra water as urine. The kidneys are also important in blood pressure regulation, and they make a hormone that tells bone marrow to create more red blood cells.
The majority (90 percent) of kidney cancers are renal cell carcinoma, or renal cell cancer. It normally involves one or a few tumors on the kidneys. Most tumors are discovered after they've developed to a significant size but before they've had time to spread (metastasize) to other areas of the body. Other types of cancerous kidney tumors include transitional cell carcinoma, Wilms tumor, and renal sarcoma.
Noncancerous (benign) tumors can develop in the kidneys. While these tumors don't spread to other areas of the body, they still can cause health problems if they grow large and put pressure on neighboring organs.
The National Cancer Institute estimates there will be more than 58,200 new cases of kidney cancer and more than 13,000 kidney cancer-related deaths by the end of 2010.
Similar to other types of cancers, kidney cancer shows few symptoms in its early stages. Symptoms of kidney cancer include:
- blood in the urine (dark yellow to brown)
- back pain
- weight loss
Kidney cancer is rare in people under the age of 45. The average age at diagnosis is 64. While there is no known cause of kidney cancer, certain risk factors have been identified:
- gender—men have a higher risk
- exposure to substances such as asbestos, cadmium, benzene, and certain herbicides.
Genetic and hereditary risk factors may also play a role in the development of kidney cancer.