Kidney cancer -- also called renal cancer -- is a disease in which kidney cells become malignant (cancerous) and grow out of control, forming a tumor. Almost all kidney cancers first appear in the lining of tiny tubes (tubules) in the kidney. This type of kidney cancer is called renal cell carcinoma. The good news is that most of kidney cancers are found before they spread (metastasize) to distant organs. And cancers caught early are easier to treat successfully. However, these tumors can grow to be quite large before they are detected.

The kidneys are two bean-shaped organs, each about the size of a fist. They lie in your lower abdomen on each side of your spine. Their main job is to clean your blood, removing waste products and making urine.