Kidney cancer is a growth of cells that starts in the kidneys. The kidneys are two bean-shaped organs, each about the size of a fist. They're located behind the abdominal organs, with one kidney on each side of the spine.

In adults, renal cell carcinoma is the most common type of kidney cancer. Other, less common types of kidney cancer can happen. Young children are more likely to develop a kind of kidney cancer called Wilms tumor.

The number of kidney cancers diagnosed each year seems to be increasing. One reason for this may be the fact that imaging techniques such as CT scans are being used more often. These tests may lead to the incidental discovery of more kidney cancers. Kidney cancer is often found when the cancer is small and confined to the kidney.

It's not clear what causes most kidney cancers.
Kidney cancer happens when cells in the kidney develop changes in their DNA. A cell's DNA holds the instructions that tell the cell what to do. In healthy cells, the DNA gives instructions to grow and multiply at a set rate. The instructions tell the cells to die at a set time. In cancer cells, the DNA changes give different instructions. The changes tell the cancer cells to make many more cells quickly. Cancer cells can keep living when healthy cells would die. This causes too many cells.

The cancer cells form a mass called a tumor. The tumor can grow to invade and destroy healthy body tissue. In time, cancer cells can break away and spread to other parts of the body. When cancer spreads, it's called metastatic cancer.

Factors that may increase the risk of kidney cancer include:

• Older Age: The risk of kidney cancer increases with age.
• Smoking Tobacco: People who smoke have a greater risk of kidney cancer than those who don't. The risk decreases after quitting.
• Obesity: People who are obese have a higher risk of kidney cancer than people who are considered to have a healthy weight.
• High Blood Pressure: High Blood Pressure, also called hypertension, increases the risk of Kidney Cancer.
• Certain Inherited Conditions: People who are born with certain inherited conditions may have an increased risk of kidney cancer. These conditions may include von Hippel-Lindau disease, Birt-Hogg-Dube syndrome, tuberous sclerosis complex, hereditary papillary renal cell carcinoma and familial renal cancer.
• Family History of Kidney Cancer: The risk of kidney cancer is higher if a blood relative, such as a parent or sibling, has had the disease.

There's no sure way to prevent kidney cancer, but you may reduce your risk if you:

• Drink alcohol in moderation, if at all: If you choose to drink alcohol, do so in moderation. For healthy adults, that means up to one drink a day for women and up to two drinks a day for men.
• Eat more Fruits and Vegetables: Choose a healthy diet with a variety of fruits and vegetables. Food sources of vitamins and nutrients are best. Avoid taking large doses of vitamins in pill form, as they may be harmful.
• Exercise most days of the week: Aim for at least 30 minutes of exercise on most days of the week. If you haven't been active lately, ask your healthcare professional whether it's OK and start slowly.
• Maintain a Healthy Weight: If your weight is healthy, work to maintain that weight. If you need to lose weight, ask a healthcare professional about healthy ways to lower your weight. Eat fewer calories and slowly increase the amount of exercise.
• Stop Smoking: Talk with your healthcare team about strategies and aids that can help you quit. Options include nicotine replacement products, medicines and support groups. If you've never smoked, don't start.
• Control High Blood Pressure: If you choose to drink alcohol, do so in moderation. For healthy adults, that means up to one drink a day for women and up to two drinks a day for men.