There are many types of cancer that can form in the kidneys. The kidneys are a pair of organs located just below the level of the ribs in the tissue behind the bowels and just to the front of and to either side of the backbone or spine. The job of the kidneys is to filter excess water and waste products from the blood. The water and waste then drain from each kidney through a tube called a ureter to the bladder and are eliminated from the body as urine through the urethra. The kidneys also produce substances that help control blood pressure and the formation of red blood cells.Several different types of cancer can develop in the kidney. Clear cell renal cell cancer, also known as renal cell carcinoma, is by far the most common type of kidney cancer in adults. Renes is the Latin word for kidney. Renal cell carcinoma accounts for about most cancers arising from the kidney. Renal cell carcinoma develops in the tubules of the kidney. Tubules are part of the filtering system.Cancer occurs when normal cells undergo a transformation. Because of this transformation, the cells grow and multiply without normal controls can damage adjacent tissues, and can spread or metastasize to other parts of the body.Cancer cells appear abnormal.As the cancer cells continue to multiply, they form a mass of abnormal cells called a cancerous or malignant tumor. (Tumors are not always cancer, as some are said to be benign. All the information about kidney tumors discussed in this article pertains to cancerous tumors.)Tumors overwhelm surrounding tissues by invading their space and taking the oxygen and nutrients they need to survive and function.Tumors are cancerous only if they are said to be composed of malignant. That means because of their uncontrolled growth, the tumors can both invade adjacent tissues and neighboring organs such as the liver, colon, or pancreas.Cancer cells may also travel to remote organs via the bloodstream or the lymphatic system (a major part of the immune system consisting of organs and lymph vessels, ducts, and nodes that transport lymph from vessels through the bloodstream).This process of invading and spreading to other organs is called metastasis. Renal cell carcinoma is most likely to metastasize to neighboring lymph nodes, the lungs, the liver, the bones, or the brain.Most renal cell carcinomas occur in people aged 50-70 years, but the disease can occur at any age. About twice as many men as women develop this cancer, and it occurs in all races and ethnic groups.Like almost all cancers, renal cell cancer is most likely to be successfully treated when it is found early.