The American Cancer Society estimates that more than 50,000 Americans are diagnosed each year with kidney cancer. The most common type of kidney cancer is renal cell carcinoma, accounting for up to 90% of cases of the disease.

Symptoms
Kidney cancer symptoms usually do not appear until the disease has progressed to a more advanced state. In fact, most often kidney cancer is detected while attempting to diagnose another condition. Symptoms of kidney cancer include:

• Blood in the urine, either seen during urination or detected by microscope
• An abdominal mass
• Pain felt on the side or lower back
• Unexplained weight loss
• Fatigue
• Swelling of the legs and ankles.

Causes
Kidney cancer develops when healthy kidney cells develop genetic mutations that cause them to grow out of control. These abnormal cells form a tumor. It's not always clear what causes this to occur, but kidney cancer has been linked to unhealthy lifestyle factors, such as, smoking and poor physical condition.

Risk Factors
Known risk factors for kidney cancer include:

• Smoking
• Being male
• Obesity
• Age over 50 years old
• High blood pressure
• Family or personal history of kidney cancer or bladder cancer
• Dialysis
• Abuse of over-the-counter pain relievers that contained phenacetin (withdrawn from the US market in 1983).

Diagnosis
Often kidney cancer is first detected when a physician either feels a mass on a kidney or when an X-ray performed for some other reason indicates the presence of a mass. When this occurs, blood tests as well as various imaging tests, such as ultrasound, CT scan and MRI, may be used to help diagnose the disease.

A kidney biopsy will confirm the presence or absence of cancer and determine what type it is. A kidney biopsy can be performed by fine needle aspiration. If cancer is found, more tests may need to be done to determine if the disease has spread to nearby tissues and organs.

Treatment
Typical treatments for kidney cancer include:

• Surgery to remove all or part of the kidney is standard treatment. People in the early stages are the best candidates for surgery. Read more about cancer surgery. 
• Ablation therapy is a procedure that destroys the tumor using either heat or freezing. 
• Targeted therapies use drugs that block and prevent the growth and spreading of malignant cells by attacking them directly or preventing the growth of blood vessels that provide tumors with the nourishment to grow.
• Radiation therapy is most often used to relieve discomfort caused by the effects of the disease. It may be used to treat the cancer itself, but is often ineffective. Read more about radiation therapy. 
• Immunotherapy, also called biologic therapy, is a treatment option for many types of kidney caner. Immunotherapy drugs stimulate the immune system to help fight cancer.
• Chemotherapy is often used along with immunotherapy or when immunotherapy is not effective, but is not considered an effective form of treatment for kidney cancer on its own. Read more about chemotherapy. 

Prevention
There are no proven methods to prevent kidney cancer, but there are steps you can take to reduce your risk:

• Quit smoking or don't start.
• Eat a well-balanced diet. Maintaining a healthy weight and a diet rich in nutrients reduces the risk factors for many cancers.
• Know what chemicals you are exposed to in the workplace. If you are exposed to fumes, dust and chemicals, you have a right to know. Talk to your employer about precautions (like wearing the proper safety equipment) to limit your exposure.