Cancer occurs when cells in the body grow out of control, producing abnormal cells that continue to divide in an uncontrolled way. There are over 200 different types of cancer, which can occur in any part of the body, and there are two main forms:

• Solid cancers – abnormal cells crowd out healthy cells, forming a lump or a tumour. This characterises many types of cancer.
• Leukaemia and lymphomas – cells dividing and multiplying abnormally but not forming tumours. Leukaemia can often be diagnosed after a routine blood test.