Scanning electron micrograph of a 'hairy cell' in 'hairy cell' leukaemia (HCL) showing surface features (ruffles & microvilli) on a B lymphocyte. It was previously thought that 'hairy cell' leukaemia was due to the malignant proliferation of histiocytic cells, but these cells are now thought to be B lymphocytes. Leukaemia is a malignant disease in which the bone marrow & other blood-forming organs overproduce certain types of white blood cells. These immature & abnormal cells suppress the normal production of white & red cells, thereby increasing susceptibility to infection. Magnification x6300 at 80x80cm size.