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A risk factor is something that affects a person's chance of having a disease such as cancer. For instance, smoking is a risk factor for several types of cancer in adults.

Lifestyle risk factors such as body weight, exercise, diet, and tobacco use play a major role in many adult cancers. But these factors usually take many years to impact cancer risk, and they are thought to have little or no effect on the risk of childhood cancers, including Wilms tumors. Most of the known risk factors for Wilms tumor cannot be controlled. They are genetic or hereditary (inherited).

A small number of children with Wilms tumor have a relative with the same cancer. These children may have inherited an abnormal gene from a parent. This gene change increases the risk of Wilms tumor, but it does not mean the child will have Wilms tumor.

There is a strong link between Wilms tumors and certain kinds of birth defects. About 1 out of 10 children with Wilms tumor also have birth defects. Most birth defects linked to Wilms tumors occur in syndromes. Syndromes are groups of symptoms or problems that are often linked to certain changes in genes. Missing or changed genes can cause Wilms tumors and other birth defects.

But most children with Wilms tumors do not have any known gene changes or birth defects. We cannot explain why they develop these tumors. There is nothing their parents could have done to prevent the cancer.

Researchers are learning more about how changes in the genes and other factors work to cause Wilms tumors and other cancers. They don't know exactly why some children get Wilms tumors, but they have made great progress in learning what happens as the kidneys form in a baby. When this process goes wrong, Wilms tumor can be the result.

The kidneys develop very early as babies grow in the womb. Sometimes a mistake happens as the kidney grows. Some of the cells don't mature. Instead, they stay like early (fetal) cells. Clusters of these early kidney cells can still be there after the baby is born. Most often, these cells will mature by the time the child is 3 or 4 years old. But if this doesn't happen, the cells may begin to grow out of control. The result could be a Wilms tumor.

Last Medical Review: 08/01/2012
Last Revised: 08/01/2012