Acute lymphoblastic leukaemia (ALL) is a malignancy originating from precursor lymphocytes of the B and T lineage. This type of leukaemia is the most common type of cancer in children (25%). The peak incidence is between 4 and 5 years of age, and it is extremely rare in adults. The aetiology of the disease is not fully understood, but it is currently thought to arise from a combination of genetic and environmental factors.