Leukaemia blood cells. Composite coloured scanning electron micrograph (SEM) of blood cells from chronic lymphocytic leukaemia, a form of cancer. The disease results from an increase in circulating levels of white blood cells (lymphocytes). This causes a reduction in red blood cells (erythrocytes, red) and other blood components. Chronic lymphocytic leukaemia may develop slowly over several years with no symptoms, but it can cause enlargement of the liver and spleen, and anaemia. Treatment in severe cases includes anti-cancer drugs and radiotherapy, with antibiotics to combat infection. Magnification: x4000 when printed at 10 centimetres wide.