Several types of cancer can develop in the kidneys. Renal cell carcinoma (RCC), the most common form, accounts for approximately 85% of all cases. In RCC, cancerous (malignant) cells develop in the lining of the kidney's tubules and grow into a mass called a tumor. In most cases, a single tumor develops, although more than one tumor can develop within one or both kidneys. Early diagnosis of kidney cancer is important. As with most types of cancer, the earlier the tumor is discovered, the better a patient's chances for survival. Tumors discovered at an early stage often respond well to treatment. Survival rates in such cases are high. Tumors that have grown large or spread (metastasized) through the bloodstream or lymphatic system to other parts of the body are more difficult to treat and present an increased risk for mortality.

The primary symptoms of RCC include the following:

• Abdominal mass or lump
• Blood in the urine (hematuria)
• Fever
• High blood pressure (hypertension)
• Pain in the side (flank) or lower back not associated with injury
• Persistent fatigue
• Rapid, unexplained weight loss
• Swelling (edema) in the legs and ankles