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What is Wilms Tumour

Also see:
Wilms Stages
  Wilms Chemotherapy & Treatments
  Future of Wilms Research and Clinical Trials
  What is Wilms Tumour Video
   Wilms Warriors Stories

Wilms tumour

A Wilms’ tumour is a type of kidney cancer, named after Dr Max Wilms who first wrote a paper about this condition in 1899.  It can also be called a nephroblastoma.

About 70-80 children in the UK develop a Wilms' tumour each year. It most often affects children under the age of five. Wilms has up to a 90% survival rate, unfortunately there are still 10% who do not respond to treatment as expected, like Bethany. 

Bethany's wish is to cure 100% of children diagnosed with Wilms Tumour. Please take a look at the menu to the right of the page for further information.

The kidneys

The kidneys are two organs that are found at the back of the abdomen. They are responsible for cleaning the blood to remove excess fluids and waste products which are then converted to urine.

A Wilms’ tumour may begin to develop in the kidneys when a baby is still inside the womb, if the cells which should have gone on to be kidney cells remain immature. If these cells do not mature they can grow to form a Wilms’ tumour.

Wilms’ tumours usually only affect one kidney, but in about 7% of cases it affects both.

Who does it affect?

Wilms’ tumours usually affect children under the age of five. 

  • Most children affected with Wilms tumour have no clear underlying cause for their disease.
  • Several small studies have suggested that certain environmental factors may be associated with a higher risk of Wilms tumour, but the results were conflicting.

A few children are born with a genetic predisposition to Wilms tumour, such as children with the following factors:

  • Congenital abnormalities:  It is well documented that certain syndromes are associated with Wilms tumour. The syndromes associated with the greatest risk of Wilms tumour are WAGR syndrome (Wilms tumour-aniridia-genitourinary malformation-retardation), Denys-Drash Syndrome, and Beckwith-Wiedemann Syndrome.
  • Familial Wilms tumour:  Approximately 1.5 percent of children with Wilms tumour have a relative who was also affected with Wilms tumour.
  • Bilateral Wilms tumour: About 7 percent of patients with Wilms tumour have multiple tumours in one or both kidneys. Having multiple tumours does not indicate tumor spread. 
  • Girls are at a slightly higher risk than boys of developing a Wilms' tumour.

What are the symptoms?

The most common symptom of a Wilms’ tumour is a swollen stomach. This can occur quite suddenly and is usually painless to your child. Most Wilms' tumours are quite large when they are found. They are very often much bigger than the kidney itself. Fortunately, even though they are large, most of them have not spread to other parts of the body. Other less common symptoms include:

  • Bleeding inside the tumour causing pain
  • Blood in the urine – found in between 15 and 20 out of every 100 children (15 to 20%) with a Wilms' tumour
  • Raised blood pressure
  • High temperature (fever) and also regular low-grade fever (37.0-37.5)
  • Loss of appetite
  • Weight loss
  • Feeling or being sick
  • Shortness of breath and cough (only if the cancer has spread to the lungs)
  • Urinary symptoms

How is it diagnosed?

The diagnosis of Wilms’ tumours usually involves a biopsy. A biopsy is where a sample of the tissue will be taken and examined under a microscope. Urine samples will be taken to check how your child’s kidneys are functioning and ultrasound or CT scans will be used to see whether the cancer has spread.

How is it treated?

The treatment of a Wilms’ tumour will depend on its size, whether or not it has spread to other parts of the body and the type of cells involved. In the USA children follow the NWTSG/COG protocol and are treated with surgery first and then chemotherapy. Children in europe are usually treated with chemotherapy to shrink the tumour and then surgery.  Research has shown negliable differences between these two approaches.

Types of Wilms' tumours

There are 2 main types of Wilms’ tumour. The cells in each type look different under a microscope. Doctors call this the histology of the tumour. The 2 types are

  • Wilms' tumour with favourable histology
  • Wilms' tumour with unfavourable histology

Unfavourable histology means that the cells look very large and not like normal kidney cells. The medical term for this is anaplasia. The cancer is less likely to be cured if there are lots of areas of anaplasia. But more than 9 out of 10 Wilms’ tumours (95%) have favourable histology. This means that there is no anaplasia and the chance of cure is high.

Several other very rare types of kidney cancers are found in children. Doctors used to group these as Wilms’ tumours with unfavourable histology but they are now grouped separately. They are treated in the same way as a Wilms' tumour but often more intensively. They are

  • Clear cell sarcoma of the kidney (CCSK)
  • Malignant rhabdoid tumour of the kidney


If possible, the tumour will be removed by surgery after a course of chemotherapy. This may involve removing part of or the entire kidney. Your child’s surgeon will aim to keep as much of the healthy kidney as possible. If Wilms’ tumours are in both kidneys then each kidney will be operated on separately.

Chemotherapy and radiotherapy

Chemotherapy involves using anti-cancer drugs to target the cancer cells. In the UK chemotherapy is given before surgery to shrink the tumour and then after surgery to stop the cancer from returning.
Radiotherapy may also be given, depending on the stage of the tumour. This involves targeting the tumour with high-energy rays.

What are the treatment side-effects?

If your child is undergoing chemotherapy, he or she may experience side-effects such as tiredness, sickness, diarrhoea and temporary hair loss. Your child may also be at greater risk of infections. Radiotherapy can also make your child feel tired and sick. He or she might experience skin irritation similar to sun burn and hair loss in the area that is being treated. Talk to your specialist or nurses about how you can manage these side-effects.

After treatment

Follow up

After your treatment is complete your child will still need to be seen regularly at an outpatient clinic. At this clinic, your child’s specialist will be looking for any signs that the cancer has returned (this is known as a relapse). They will also check that your child’s major organs, such as the heart and lungs, are still functioning correctly and haven’t been affected by the cancer treatment.

Long-term follow up

Once your child’s risk of relapse has reduced, the focus of on-going follow up changes to looking out for potential long term side effects of treatment. The risk of long term side effects depends on the type of cancer your child had and the treatment received. A personalised surveillance plan is usually created that outlines the specific long term follow up and on-going investigations that your child will require. Many people are at low risk of future health problems but some will have significant on-going health needs. Talk to your child’s specialist about the potential long-term side-effects of their treatment.

Long-term side-effects

When one kidney has been removed, the other will still function normally and will take over the work of the kidney that has been removed. Because Wilms’ tumours usually occur in one kidney only, very few children go on to have long-term kidney problems. Other late effects can include:

  • Heart or lung problems after receiving certain chemotherapy drugs or radiation therapy to these parts of the body
  • Slowed or decreased growth and development
  • Changes in sexual development and ability to have children (especially in girls)
  • Development of second cancers later in life (rare) 

Sources for Information 

Clic Sargent 

Cancer Research UK


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