Wilms tumour (nephroblastoma): symptoms, diagnosis and treatment in children

Wilms tumour is a cancer of the kidney that develops in childhood. CCLG explains that it is named after Dr Max Wilms, who first described it, and that its other name is nephroblastoma. It is thought to develop from immature cells that take part in the development of the kidneys while a baby is in the womb.

Cancer Research UK says that when a baby grows in the womb the kidneys develop very early and that sometimes immature cells (nephroblasts) do not develop into mature kidney cells, then begin to grow out of control. It says Wilms tumours usually affect only one kidney, but in fewer than 10 out of every 100 children they can affect both.

It is uncommon. Cancer Research UK says about 85 children aged 0 to 14 are diagnosed each year in the UK and that Wilms tumour is most common in children under 5, and rarely it can develop in older children and very rarely in adults. CCLG gives a slightly different framing, saying it most often affects children under seven.

The cause is not known. CCLG stresses that nothing a parent has done has caused their child’s cancer. Cancer Research UK says some Wilms tumours have changes in specific genes, but it is not clear why those changes happen.

A small number of children have another condition present from birth. Cancer Research UK says about 8 in 100 children who develop a Wilms tumour also have another condition that may be present at birth, linked with rare syndromes such as WAGR syndrome, Beckwith-Wiedemann syndrome and Denys-Drash syndrome. CCLG lists the lack of an iris in the eye (aniridia), abnormalities of the genitals and a condition in which one side of the body is slightly larger than the other (hemihypertrophy).

A family history is uncommon. CCLG says it is present in only 1 to 2 per cent of cases, and Cancer Research UK gives about 2 in 100. Cancer Research UK adds that children at higher risk may be offered screening, usually with regular ultrasound scans, which aims to find a tumour early but does not prevent it.

Cancer Research UK says most Wilms tumours are quite large when found, and most have not spread. The commonest sign is a painless swollen tummy. Other symptoms are listed below. It stresses that Wilms tumour is very rare and that having these symptoms does not mean a child has cancer, but that it is important to take them to the GP so any problems can be looked into.

• A painless swelling or lump in the tummy, sometimes noticed in the bath or when clothes no longer fit.

• Blood in the urine.

• Pain, if the tumour bleeds inside.

• Raised blood pressure.

• A high temperature, loss of appetite, weight loss, constipation or generally feeling unwell.

• Shortness of breath and cough, usually if the cancer has spread to the lungs.

CCLG says an ultrasound scan of the tummy is usually the first test, followed by an MRI scan and/or CT scan of the tummy and chest to show where the tumour is and whether it has spread beyond the kidney. Urine and blood samples check how well the kidneys are working. Some children go on to have a biopsy, depending on the medical team’s assessment.

Stage describes the size of the cancer and whether it has spread. CCLG says that for Wilms tumour the stage is finalised after surgery, and that because most children have chemotherapy first, the exact stage may not be known straight away. Babies under six months usually have surgery straight away.

CCLG says the main treatments are chemotherapy and surgery, with radiotherapy for some children. Treatment depends on the stage and on the risk group, based on how the tumour looks under the microscope. Most tumours are in the standard-risk group. Low-risk tumours need less treatment, while high-risk types, anaplastic and blastemal, need more intensive chemotherapy.

Surgery involves removing the affected kidney (nephrectomy). CCLG says most people can live normally with only one kidney remaining. When both kidneys are affected, which CCLG puts at about 1 in 20 cases, treatment usually involves surgery to both with the aim of removing as much cancer as possible while leaving as much healthy kidney as possible, and chemotherapy is always given.

In the UK, many children are treated within clinical trials. CCLG says that where no trial is available, doctors use guidelines agreed by experts across the UK. Treatment is delivered at specialist children’s cancer centres, so families are usually referred from their local hospital to a principal treatment centre.

CCLG says about 90 per cent of children with Wilms tumour are successfully treated, and that if the cancer comes back a different course of treatment can be given. Cancer Research UK says relapse is rare, is most likely in the first 2 years after treatment, and is more common in children whose cancer had spread to distant parts of the body or whose cells looked very abnormal under a microscope.

Regular follow-up appointments continue after treatment. Cancer Research UK says all children have at least 5 years of follow-up, with appointments gradually getting further apart, and that very few have long-term side effects from treatment or from having one kidney. Possible long-term issues it lists include changes to how the heart works after doxorubicin, kidney function problems, hearing problems after carboplatin, a very small risk of a second cancer and a risk of reduced fertility after cyclophosphamide. Long-term follow-up clinics are available.

Care in the UK is provided through the NHS, with voluntary organisations such as CCLG and Cancer Research UK providing information and support for families. Practical and emotional support for parents and siblings is part of the care team’s role.