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Wilms tumour

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What is Wilms tumour?

Wilms tumour is a malignant tumour that starts in the cells of the kidney. Malignant means that it can spread, or metastasize, to other parts of the body. Wilms tumour is the most common type of kidney cancer in children.

The kidney is part of the urinary system. There are 2 kidneys, one either side of the backbone, deep inside the upper part of the abdomen. The kidneys make urine by filtering water and waste from the blood.

Cells in the kidney sometimes change and no longer grow or behave normally. These changes may lead to benign tumours such as congenital mesoblastic nephroma, which develops in very young children. Benign tumours are not cancerous.

Changes to cells of the kidney can also cause precancerous conditions. This means that the cells are not yet cancer but there is a higher chance these abnormal changes will become cancer. The most common precancerous condition of the kidney is nephroblastomatosis. In some cases, changes to kidney cells can cause Wilms tumour.

Wilms tumour develops from changes in an immature (embryonic) kidney cell. It is usually found in children aged 2–4 years.

Rare types of kidney cancer can also develop in children. These include clear cell sarcoma, rhabdoid tumour and renal cell carcinoma.

Diagram of the location of the kidneys


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