There are two kidneys located on either side of the spine at the bottom of the rib cage. They clean the blood by removing excess fluids and waste products, which are then removed from the body through urine.
Wilms tumour was named after Dr Max Wilms, who first described it. The other name for this tumour is nephroblastoma. It is thought to develop from immature cells in the embryo. These cells are involved in the development of the child’s kidneys while they are in the womb.
The cells usually disappear at birth, but in many children with Wilms tumour, clusters of these kidney cells, called nephrogenic rests, can still be found.
Watch our expert Dr James Nicholson, Paediatric Oncologist and CCLG member, explain more about Wilms tumour.
Causes
It is not known what causes Wilms tumours. Very rarely, people who develop a Wilms tumour have other specific conditions which are present at birth (congenital malformations). These include the lack of an iris in the eye (aniridia), abnormalities of the genitals, and a condition where one side of the body is slightly larger than the other (hemihypertrophy). A family history is present in only 1-2% of cases and therefore it is unlikely to be passed down through family members. It is important to remember that nothing you have done has caused your child’s cancer.
Signs and symptoms
The most common symptom is a swollen abdomen, which is usually painless. Sometimes a parent or carer may feel a lump in the abdomen which can be quite large.
Occasionally, the tumour may bleed slightly and this can irritate the kidney and may be painful. There may be blood in your child’s urine, or their blood pressure may be raised. The child may also have a high temperature (fever), upset stomach, weight loss or a lack of appetite.
How Wilms tumour is diagnosed
Your child may need a variety of tests and investigations to diagnose a Wilms tumour. These will be explained to you by your child’s medical team.
An ultrasound scan of the tummy (abdomen) is usually the first thing that is done. This will be followed by an MRI and/or CT scan of the tummy and chest. These scans help doctors to identify exactly where the tumour is and whether it has spread beyond the kidney. Urine and blood samples will also be taken to check how well your child’s kidneys are working. Some children will go on to have a biopsy, where a sample of tissue is taken from the tumour to confirm the diagnosis. This will depend on the medical team’s assessment of your child along with results of scans and other tests.
Staging
The stage of a cancer is a term used to describe its size and whether it has spread beyond the kidney. The treatment your child receives depends on the stage of the disease. In the case of Wilms tumour, the stage is finalised after surgery to remove the tumour. As most Wilms’ tumour patients receive chemotherapy before surgery, you may not know the exact stage of your child’s tumour straight away. An exception is that babies under six months old usually have surgery straight away.
The staging system commonly used is described below:
- Stage 1 - the tumour is only affecting the kidney and has not begun to spread. It can be completely removed with surgery.
- Stage 2 - the tumour has begun to spread beyond the kidney to nearby structures, but it’s still possible to remove it completely with surgery.
- Stage 3 - the tumour has spread beyond the kidney; either because the tumour has burst before (or during) the operation, has spread to lymph glands (nodes) in the tummy (abdomen), or has not been completely removed by surgery.
- Stage 4 - the tumour has spread to other parts of the body such as the lungs or liver. Tumours in other parts of the body are known as metastases.
- Stage 5 - there are tumours in both kidneys (bilateral Wilms tumour).
Treatment
The main treatment for Wilms tumour is chemotherapy and surgery. Some children will also need radiotherapy. Your child’s treatment will depend on the type and stage of the disease. Your child’s doctor will discuss the treatment options with you.
Surgery
All children with Wilms tumour will have surgery. In a few cases, this may also involve taking a small sample of cells from the tumour to confirm the diagnosis. This is called a biopsy and is usually done under a general anaesthetic. Apart from very young children (under six months), most children will receive chemotherapy before having an operation to remove the entire tumour. The operation usually involves removing the whole of the affected kidney (nephrectomy). Most people can live normally with only one kidney remaining.
Wilms tumours can be divided into a number of risk groups based on what they look like under the microscope. This tells doctors how they are likely to behave. The treatment following surgery will depend on these risk groups. The risk groups are known as low, standard (or intermediate), and high.
Most tumours are in the ‘standard risk’ group. ‘Low risk’ tumours require less treatment than ‘standard risk’ tumours.
There are two types of high-risk Wilms tumour - anaplastic and blastemal – which require more intensive (stronger) chemotherapy:
- Anaplastic Wilms tumour
About 5-10% of Wilms’ tumours have an appearance called anaplasia, which means the cells look very disorganised under a microscope. - Blastemal Wilms tumour
This group of high-risk tumours cannot be identified by looking at the biopsy because they occur when a particular type of early kidney cell survives the pre-surgery chemotherapy. These cells are known as blastemal cells. Tumours where most of these cells survive chemotherapy are called 'blastemal-type' tumours.
Other kidney tumours
Other, less common types of kidney tumours may occur in children. These are usually only recognised after surgery to obtain a tumour sample. ‘Clear cell sarcoma’ and ‘malignant rhabdoid tumour’ of the kidney are two types of cancerous tumour, with their own treatment recommendations.
Congenital mesoblastic nephroma is a non-cancerous (benign) tumour that occurs in very young children; this type of tumour usually only needs surgery and no other treatment.
Chemotherapy
Chemotherapy is the use of anti-cancer drugs to destroy cancer cells. It’s usually given as an injection or drip into a vein (intravenously). Chemotherapy is given before surgery (pre-operative chemotherapy) to shrink the tumour and make it easier to remove.
By looking at what the tumour cells look like under the microscope and how far the cancer has spread, doctors can decide whether additional chemotherapy should be given to help reduce the risk of the cancer coming back.
The drugs used and the length of the chemotherapy depends on the stage and risk group of the tumour.
Radiotherapy
Radiotherapy treats cancer by using high-energy rays to destroy the cancer cells.
Not all children with Wilms tumour need radiotherapy. For those who do, the area to be treated depends on the stage of the tumour at diagnosis. Some children have radiotherapy to the area around the affected kidney or, less commonly, to the whole abdomen. If the tumour has spread to the lungs, then lung radiotherapy may be needed but this depends on how well the cancer responds to initial chemotherapy.
Radiotherapy is occasionally used to shrink tumours that are too large to remove surgically with the aim of allowing an operation to be done. Radiotherapy may be used when tumours have spread elsewhere in the body.
Treatment for bilateral Wilms’ tumour
In about 1 in 20 cases, Wilms tumour affects both kidneys. Treatment usually involves surgery to both. The aim of the treatment is to remove as much of the cancer as possible, while leaving as much healthy kidney as possible. Chemotherapy is always given. Sometimes radiotherapy is needed as well.
Clinical trials
Many children have their treatment as part of a clinical research trial. Clinical trials are carried out to try to improve our understanding of the best way to treat an illness, usually by comparing the standard treatment with a new or modified version. Clinical trials mean there are now better results for curing children’s cancers compared with just a few years ago.
Your child’s medical team will talk to you about taking part in a clinical trial and will answer any questions you have. Taking part in a research trial is completely voluntary, and you’ll be given plenty of time to decide if it’s right for your child. You may decide not to take part, or you can withdraw from a trial at any stage. You will then receive the best standard treatment available.
National treatment guidelines
Sometimes, clinical trials are not available for your child’s tumour. In these cases, your doctors will offer the most appropriate treatment, using guidelines which have been agreed by experts across the UK. Children’s Cancer and Leukaemia Group (CCLG) is an important organisation which helps to produce these guidelines.
Relapse
About 90% of children with Wilms tumour are successfully treated. If the cancer comes back, a different course of treatment can be given. Your child’s doctor will discuss all the options with you. You may find the publication Treatment options for relapsed Wilms tumour in children useful.
Follow-up care
Once treatment has finished, the doctors will monitor your child closely with regular appointments to be sure that the cancer has not come back. Very few children have long-term kidney problems. After a while, you will not need to visit the clinic so often.
If you have specific concerns about your child’s condition and treatment, it’s best to discuss them with your child’s doctor, who knows the situation in detail.
Useful resources
A parent's guide to kidney tumours (CCLG 2022)
Treatment options for relapsed Wilms tumour in children (2022)