Acute leukemia is characterized by proliferation
of immature cells or blasts in the bone marrow, and commonly
involves the peripheral blood and other organs.
The acute leukemias can be classified using the French, American,
and British (FAB)* Classification (1975;1985 revision) in which
acute nonlymphoid leukemias are subdivided into 7 types, and lymphoid
leukemias are subdivided into 3 types. This classification system
is very helpful for the student first learning about the acute
The current standard for classifying the acute leukemias is the
World Health Organization (WHO) classification system. The WHO system
takes into account morphology, cytogenetics, molecular genetics,
and immunologic markers to create a classification system that is
uuniversally applicable and prognostically significant.
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