Leukaemia is a cancer that starts in
blood-forming tissue.
There are different types of leukaemia.
Those that develop suddenly (over days or weeks) are called
acute leukaemias. Leukaemias that develop over months or years
are chronic leukaemias.
Leukaemia is also named by the type of white blood cell affected, either the
myeloid or lymphoid cells, which are distinguished by their appearance under the
microscope.
Myeloid white blood cells are the immune system's first line
of defence against infection and are found mainly in the blood. [They] engulf
and kill foreign organisms. Lymphoid white blood cells are
found in the lymph nodes and in the blood. They lie in wait to detect foreign
organisms and stimulate the body's defences to fight them.
[CLL leukemia is Chronic Lymphoid Leukaemia. Non-CLL leukemia refers to any
other type of leukemia, that is, chronic myeloid, acute myeloid or acute
lymphoid leukemia]
