A risk factor is anything that affects the chance of having a disease such as cancer. Different cancers have different risk factors. For example, exposing skin to strong sunlight is a risk factor for skin cancer.

But risk factors don't tell us everything. Having a risk factor, or even several, does not mean that a person will get the disease, and many people get cancer without having any known risk factors.

Although lifestyle-related risks (such as smoking and obesity) are significant factors in many cancers of adults, they tend to have little or no effect on childhood cancer risk. For most Wilms tumors these is no clear cause.

Environmental risk factors

So far research has not found any strong links between Wilms tumor and environmental factors, either before or after a child's birth.

Genetic and hereditary risk factors

Family history of Wilms tumor

Between 1% and 3% of children with Wilms tumors have one or more relatives with the same cancer. Scientists think that these children inherit chromosomes with an abnormal or missing gene from a parent that increases their risk of developing Wilms tumor.

Children with these familial cases of Wilms tumors are slightly more likely than children with sporadic cases (no relatives with Wilms tumor) to have tumors in both kidneys. But most familial cases affect only 1 kidney.

Certain inherited syndromes/birth defects

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, signs, malformations, or other abnormalities that occur together in the same person. Those linked to Wilms tumor include:

WAGR syndrome: Children with this syndrome have about a 50% chance of having a Wilms tumor. It is caused by the loss (deletion) of part of chromosome 11, where the WT1 gene is normally found. WAGR stands for:

• Wilms tumor
• Aniridia (complete or partial lack of the iris [colored area] of the eyes)
• Genitourinary tract abnormalities (defects of the kidneys, urinary tract, penis, scrotum, clitoris, testicles, or ovaries)
• mental Retardation

Beckwith-Wiedemann syndrome: Children with this syndrome tend to be big for their age. They also have larger than normal internal organs and often have an enlarged tongue. They may have an oversized arm and/or leg on one side of the body (hemihypertrophy), as well as other medical problems. They have about a 5% to 10% risk of having Wilms tumors.

Denys-Drash syndrome: This rare syndrome has been linked to changes (mutations) in the WT1 gene. In this syndrome the kidneys become diseased and stop working when the child is very young. Wilms tumors usually develop in the diseased kidneys. The reproductive organs do not develop normally. In boys, the penis, testicles, and scrotum do not develop, which may cause them to be mistaken for girls. Because the risk of Wilms tumors is very high, most doctors advise removing the kidneys soon after this syndrome is diagnosed.

Other syndromes or birth defects: Less often, Wilms tumor has been linked to other syndromes, including:

• Perlman syndrome
• Sotos syndrome
• Simpson-Golabi-Behmel syndrome
• Bloom syndrome

Wilms tumor is also more common in children with certain birth defects:

• aniridia (complete or partial lack of the iris [colored area] of the eyes)
• hemihypertrophy (an oversized arm and/or leg on one side of the body)
• cryptorchidism (failure of the testicles to descend into the scrotum) in boys
• hypospadias (defect in boys where the urinary opening is on the underside of the penis)

Other risk factors

Race

In the United States, the risk of having Wilms tumor is slightly higher in African-American children than in white children and is lowest among Asian-American children. The reason for this is not known.

Sex

The risk of having Wilms tumors is slightly higher in girls than in boys.

Last Medical Review: 09/14/2009
Last Revised: 09/14/2009