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Wilms' tumour

Find out about Wilms' tumours in children, and how it is treated. 

What it is

Wilms’ tumour (also called nephroblastoma) is a type of kidney cancer that affects children. It’s named after Dr Max Wilms, who wrote the first medical paper about it.

When a baby is growing in the womb, the kidneys develop very early on. Sometimes some cells that should have turned into mature kidney cells fail to do so. Instead they stay as very immature cells.

Often these immature cells mature by the time the child is 3 or 4. But if they don’t, they begin to grow out of control and may develop into a cancer known as a Wilms’ tumour.

How common it is

Kidney cancer is rare in children but this is the most common type they get. Around 80 children are diagnosed with a Wilms' tumour each year in the UK. It is most common in children under 5. Rarely, it can appear in older children and adults.

Wilms’ tumours usually only affect one kidney (unilateral). But in about 10 out of every 100 children (10%) it can affect both (bilateral).

Risks and causes

The causes of Wilms’ tumours are unknown. But several risk factors have been identified.


Girls are at a slightly higher risk than boys of developing a Wilms' tumour.

Birth defects

Certain genetic mutations that cause birth defects can increase your risk of developing a Wilms' tumour. About 5 out of every 100 children (5%) who develop a Wilms' tumour also have a birth defect.

Most birth defects associated with Wilms' tumours happen in syndromes. A syndrome is a group of symptoms and abnormalities that are present in the same person.

Gene mutations affect all body cells. So children born with one of these syndromes can have several parts of their body affected and not just their kidneys. These syndromes are very rare. The main ones are:

WAGR syndrome – a combination of abnormalities in the coloured part of the eye (iris), the genitourinary tract and the brain. The iris is either partly or totally missing (aniridia). There can be defects in the kidneys, urinary system, penis, scrotum, clitoris, testicles or ovaries. And the person may have learning disability.

Beckwith-Wiedemann Syndrome – children have larger than normal internal organs and often have a very big tongue. Also, one arm or leg may be bigger than the other.

Denys-Drash Syndrome – affected boy babies do not develop a penis, scrotum or testicles and can be mistaken for girls. They also develop damaged kidneys that stop working. A Wilms' tumour can grow in the damaged kidney.

Family history

Between 1 and 2 out of every 100 children (1 to 2%) with a Wilms' tumour have at least one relative who has had the same type of cancer. These children are at an increased risk of developing a Wilms' tumour because they have inherited an abnormal gene from one of their parents.

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 (this is called anaplasia). The cancer is less likely to be cured if there are lots of areas of anaplasia.

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


Most Wilms' tumours are quite large when they’re found. They are very often much bigger than the kidney itself. Fortunately, most of them have not spread to other parts of the body. 

The most common symptom is a painless swelling of the abdomen. Parents may notice this if their child suddenly jumps a nappy size.

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)
  • loss of appetite
  • weight loss
  • feeling or being sick
  • shortness of breath and cough (only if the cancer has spread to the lungs)

Referral to a specialist

A GP should refer your child to a specialist urgently – within 2 days – if there are any of the following symptoms:

  • a lump in the tummy (abdomen) that they can feel
  • an enlarged organ in the tummy
  • blood in the urine


The treatment for a Wilms’ tumour depends on the size of the cancer and whether it has spread to nearby lymph nodes.

This type of tumour is very rare, so it is treated in specialist centres – usually a major children's cancer centre. These centres have teams of specialists who know about Wilms’ tumours and the best way to treat them. 

The main treatments include surgery, radiotherapy and chemotherapy.


All children have surgery to remove the affected kidney (called a nephrectomy). The surgeon removes the whole kidney with the tissues around it, including the adrenal gland and some lymph nodes in the area. The adrenal gland is attached to the kidney. 

Some surgeons remove the tumours using keyhole surgery. This means the surgeon makes a few small cuts in the skin over the kidney rather than one larger wound. Your child's surgeon will discuss with you which type of surgery is best in their case.

Chemotherapy or radiotherapy

Sometimes the tumour may be too big to remove, or may have spread to nearby areas or to both kidneys. If this is the case your doctor may give cancer killing drugs (chemotherapy) before surgery. 

To treat Wilm's, doctors often use the following chemotherapy drugs: 

  • vincristine
  • dactinomycin
  • doxorubicin

Your child may need radiotherapy before surgery to shrink the tumour before they have an operation. 

After surgery, some children may have chemotherapy, radiotherapy or both. This treatment is to kill off any cancer cells left behind. Radiotherapy is given from an external machine.

Research and clinical trials

Researchers are looking at different combinations of chemotherapy drugs to treat Wilms' tumour. And as more children get better from their Wilms' tumour, doctors are studying the long term effects of chemotherapy and radiotherapy treatments.

Getting support and information

Parents have a lot to think about and are likely to be very worried about getting the best treatment for their child. Feeling frightened about your child having cancer is normal.

The good news is that Wilms' tumour is curable in more than 9 out of 10 children (90%) diagnosed. Talk to the doctors about any worries that you have. They will understand and will want you to feel comfortable and confident with the treatment and care that your child is getting.

Our page about children's cancer organisations gives details of organisations you can contact for information, help and support.

Cancer Research UK has an online forum called Cancer Chat. You may find it helpful to join the forum to talk to other people whose children or relatives have cancer.

You can also contact the Cancer Research UK information nurses on freephone 0808 800 4040. The lines are open from 9am until 5pm, Monday to Friday.
Last reviewed: 
24 Feb 2016
  • Suspected cancer: recognition and referral 
    The National Institute for Health and Care Excellence (NICE), June 2015

  • Laparoscopic treatment of renal cancer in children: a multicentric study and review of oncologic and surgical complications
    F Varlet and others
    Journal of Pediatric Urology, 2014, Volume 10, Issue 3, Pages 500-5

  • Wilms' tumor: biology, diagnosis and treatment
    E Szychot and others
    Translational Pediatrics 2014, Volume 3, Issue 1, Pages 12-24

  • Cancer: Principles and Practice of Oncology (10th edition)
    VT De Vita, TS Lawrence and SA Rosenberg
    Lippincott, Williams and Wilkins, 2015

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