What Is Kidney Cancer?

The kidneys are two bean-shaped organs in the low back area that are responsible for filtering waste and excess fluid from your blood. Kidney cancer begins when normal cells in one or both kidneys begin to change and grow uncontrollably, forming a mass called a tumor. A tumor can be benign (noncancerous) or malignant (cancerous, meaning it can spread to other parts of the body). Kidney cancer is also referred to as renal cancer.

More than 50,000 people are diagnosed with kidney cancer each year. The exact cause of kidney cancer is unknown, but it is associated with certain risk factors such as smoking, family history of kidney cancer, long-term dialysis, high blood pressure and other diseases. Men are twice as likely to develop kidney cancer than women.