What is it?
Named after Dr Max Wilms, these renal tumours are thought to develop from cells that are present at the embryo stage.
When the kidneys develop in the womb, cells called metanephric blastema, which usually disappear after birth, remain present. They start to grow out of control, forming a mass of small immature cells.
Wilms’ tumour usually only affects one kidney (unilateral) but, in rare cases, can affect both (bilateral).