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Wilms tumour

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Risk factors for Wilms tumour

A risk factor is something that increases the risk of developing cancer. It could be a behaviour, substance or condition. Most cancers are the result of many risk factors. But sometimes Wilms tumour develops in children who don’t have any of the risk factors described below.

Most Wilms tumours are diagnosed in children younger than 5 years of age. The average age at diagnosis is between 2 and 4 years old. Wilms tumours develop slightly more often in children of African ancestry and less often in children of Asian ancestry. They develop slightly more often in girls than boys.

The following are risk factors for Wilms tumour. All of the known risk factors are not modifiable. This means that you can’t avoid them. Until we learn more about these risk factors, there are no specific ways you can reduce the risk.

Risk factors are generally listed in order from most to least important. But in most cases, it is impossible to rank them with absolute certainty.

Known risk factors

Experts believe that Wilms tumour is caused by changes, or mutations, in certain genes. A gene is the basic unit of heredity passed from parents to a child. A genetic condition is a set of symptoms that occur together and are usually caused by one or more abnormal genes. Having certain genetic conditions can increase the risk of developing Wilms tumour. About 5%–10% of children diagnosed with Wilms tumour have a genetic condition.

Wilms tumour is also more common in children with certain birth defects, or congenital abnormalities. About 10% of children with Wilms tumour have a congenital abnormality.

There is convincing evidence that the following factors increase the risk for Wilms tumour.

WAGR syndrome

WAGR syndrome is a rare genetic condition. It is caused by loss or inactivation of a tumour suppressor gene. Tumour suppressor genes usually control cell growth and stop tumours from growing. When these genes aren’t present or don’t work properly, they no longer control cell growth and tumours may form.

WAGR stands for the 4 conditions present in WAGR syndrome:

  • Wilms tumour
  • aniridia, which is when the coloured part of the eye (iris) doesn’t form completely
  • genitourinary malformations, which is when the reproductive and urinary systems don’t form normally
  • mental retardation

Most people who have WAGR syndrome have 2 or more of these conditions. But not all people with WAGR syndrome will develop Wilms tumour. Children with WAGR syndrome have a 25%–30% chance of developing it.

Beckwith-Wiedemann syndrome

Beckwith-Wiedemann syndrome is a genetic condition that causes the body and some organs, such as the tongue, liver and spleen, to grow larger than normal. It also affects the belly in babies so that the abdomen doesn’t close around the base of the umbilical cord. As a result, the organs stick out into the base of the cord. This is called an omphalocele.

Children with Beckwith-Wiedemann syndrome have a 5% risk of developing Wilms tumour.

Denys-Drash syndrome

Denys-Drash syndrome is a genetic condition that causes kidney disease at birth and Wilms tumour. It also affects the sex organs so they don’t form properly.

Almost all children with Denys-Drash syndrome develop Wilms tumour in one or both kidneys. It is usually diagnosed around 2 years of age.

Simpson-Golabi-Behmel syndrome

Simpson-Golabi-Behmel syndrome is a genetic condition found mostly in boys. It affects many parts of the body. Babies with Simpson-Golabi-Behmel syndrome are much larger than normal at birth, and they grow and gain weight at an unusual rate.

About 10% of children with Simpson-Golabi-Behmel syndrome will develop benign or cancerous tumours during childhood. The most common of these cancers is Wilms tumour.

Bloom syndrome

Bloom syndrome is a rare inherited condition caused by a large number of abnormal chromosomes. People with Bloom syndrome are usually smaller than average, have a high-pitched voice and a characteristic facial appearance. They also have a higher risk of developing different types of cancer, including Wilms tumour.

Perlman syndrome

Perlman syndrome is a very rare genetic condition. It is very similar to Beckwith-Weidemann syndrome. During pregnancy, there is too much fluid in the uterus. As a result, the baby may be born larger and heavier than normal, with abnormal facial features.

Babies and children with Perlman syndrome have a very high risk for Wilms tumour.

Frasier syndrome

Frasier syndrome is a very rare genetic condition. In boys, Frasier syndrome affects both kidneys and it causes genitals to not form properly. In girls, it usually only affects the kidneys.


Aniridia is a rare birth defect in which the coloured part of the eye (iris) doesn’t form completely. The iris controls the amount of light entering the eye. Aniridia can cause blindness.


Hemihypertrophy is a birth defect that causes part or one side of the body to grow larger than the other.

Undescended testicles

Undescended testicles, or cryptorchidism, is a common birth defect in boys. It means that one or both testicles do not drop down (descend) into the scrotum.


Hypospadias is a birth defect in boys. It occurs when the urinary (urethral) opening is on the underside of the penis rather than at the tip.

Family history

A small number of Wilms tumours develop in children who have family members with the disease. About 1%–2% of children diagnosed with Wilms tumour have a family history of the disease.

Possible risk factors

Being heavier than 4 kilograms (about 9 pounds) at birth is a possible risk factor for Wilms tumour, especially for girls. This means that a higher birth weight has been linked with Wilms tumour, but there is not enough evidence to show that it is a known risk factor.

Unknown risk factors

It isn’t known whether or not the following factors are linked with Wilms tumour. It may be that researchers can’t show a definite link or that studies have had different results. Further study is needed to see if the following are risk factors for Wilms tumour:

  • the child’s or a parent’s exposure to pesticides
  • father’s exposures to certain industrial chemicals or metals
  • mother’s exposure to hair dyes or certain medicines during pregnancy or birth

Questions to ask your healthcare team

Ask your child’s healthcare team questions about risks.


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