Wilms tumour, also known as nephroblastoma, is a cancer that develops in the kidneys from the abnormal growth of early kidney cells. Although Wilms tumours most commonly affect only one kidney, in some instances there may be more than one tumour in the same kidney or tumours in both kidneys.

Wilms tumours are also classified based on their histology:

• Favourable histology – the cancer cells do not have anaplasia (where the centre of the cells, known as nuclei, are very large and distorted). The chance of curing these tumours is very high
• Anaplastic histology – the cancer cells have anaplasia. Tumours that have anaplasia throughout (diffuse anaplasia) are harder to treat than those with anaplasia contained in certain parts of the tumour (focal anaplasia)

According to the Singapore Childhood Cancer Registry, renal tumours are the ninth most common childhood cancer in Singapore with Wilms tumours accounting for 2.1% of all childhood cancer diagnoses. Wilms tumour is the most common type of kidney cancer in children.

The most common symptom of Wilms tumours in children is a large swelling, mass or lump in the abdomen, as tumours often grow quite large before causing signs and symptoms.

Other symptoms may include:

• Abdominal pain
• Fever
• Blood in urine
• Nausea or vomiting
• Loss of appetite
• High blood pressure
• Shortness of breath
• Constipation