Leukemia is defined as the uncontrolled proliferation of abnormal leukocytes in the blood and bone marrow. By the type of white blood cells affected leukemia is classified in:
- Lymphocytic leukemia (also known as lymphoid or lymphoblastic leukemia) develops in the lymphocytes in the bone marrow.
- Myeloid leukemia (also known as myelogenous leukemia) may also start in white blood cells other than lymphocytes, as well as red blood cells and platelets.
In terms of how quickly it develops or gets worse, leukemia is also classified as either acute (fast-growing) or chronic (slow-growing)