The following is provided by the National Cancer Institute

Each year, more than 50,000 people in the United States learn that they have kidney cancer. Several types of cancer can develop in the kidney. Renal cell cancer is the most common form of kidney cancer in adults. Transitional cell cancer (carcinoma), which affects the renal pelvis, is a less common form of kidney cancer. It is similar to cancer that occurs in the bladder and is often treated like bladder cancer.

As kidney cancer grows, it may invade organs near the kidney, such as the liver, colon or pancreas. Kidney cancer cells may also break away from the original tumor and spread (metastasize) to other parts of the body.

Kidney cancer develops most often in people over 40, but no one knows the exact causes of this disease. Doctors can seldom explain why one person develops kidney cancer and another does not.

Research has shown that people with certain risk factors are more likely than others to develop kidney cancer. Studies have found the following risk factors for kidney cancer:

Smoking: Cigarette smoking is a major risk factor. Cigarette smokers are twice as likely as nonsmokers to develop kidney cancer. Cigar smoking also may increase the risk of this disease.

Obesity: People who are obese have an increased risk of kidney cancer.

High blood pressure: High blood pressure increases the risk of kidney cancer.

Long-term dialysis: Dialysis is a treatment for people whose kidneys do not work well. It removes wastes from the blood. Being on dialysis for many years is a risk factor for kidney cancer.

Von Hippel-Lindau (VHL) syndrome: VHL is a rare disease that runs in some families. It is caused by changes in the VHL gene. An abnormal VHL gene increases the risk of kidney cancer. It also can cause cysts or tumors in the eyes, brain and other parts of the body. Family members of those with this syndrome can have a test to check for the abnormal VHL gene. For people with the abnormal VHL gene, doctors may suggest ways to improve the detection of kidney cancer and other diseases before symptoms develop.

Occupation: Some people have a higher risk of getting kidney cancer because they come in contact with certain chemicals or substances in their workplace. Coke oven workers in the iron and steel industry are at risk. Workers exposed to asbestos or cadmium also may be at risk.

Gender: Males are more likely than females to be diagnosed with kidney cancer. Each year in the United States, about 20,000 men and 12,000 women learn they have kidney cancer.

Most people who have these risk factors do not get kidney cancer. On the other hand, most people who do get the disease have no known risk factors. People who think they may be at risk should discuss this concern with their doctor. The doctor may be able to suggest ways to reduce the risk and can plan an appropriate schedule for checkups.

When kidney cancer spreads, cancer cells may appear in the lymph nodes. For this reason, lymph nodes near the kidney may be removed during surgery. If a pathologist finds cancer cells in your lymph nodes, it may mean that the disease has spread to other parts of the body. Kidney cancer may spread and form new tumors, most often in the bones or lungs. The new tumors have the same kind of abnormal cells and the same name as the original (primary) tumor in the kidney. For example, if kidney cancer spreads to the lungs, the cancer cells in the lungs are kidney cancer cells. The disease is metastatic kidney cancer; it is not lung cancer.