Acute lymphoblastic leukemia (ALL) is a malignant disease of the bone marrow, characterized by the proliferation of lymphoid precursor cells. These precursor cells increase to a large enough number that cause a replacement of the normal bone marrow elements, causing anemia, thrombocytopenia, and neutropenia. Proliferation of the lymphoblasts also occurs in the liver, spleen, lymph nodes, and other organs. ALL is the most common type of pediatric cancer. The major cause of this cancer is thought to be exposure to high levels of radiation and/or carcinogens, such as benzene. About 5% of ALL cases are due to related genetic disorders, such as Down's syndrome. Chromosomal rearrangements are the causative factor in a majority of the cases.
A confirmed diagnosis of ALL requires the visualization of the abnormal proliferation of lymphocytes in the blood and bone marrow samples. This test is also used to categorize ALL into types. Lumbar punctures are used to detect the presence of leukemic cells in the CSF. Patients are usually treated with a combination of chemotherapy, radiation therapy, and if necessary, a bone marrow transplant. Surgery is not an option for ALL. The chemotherapy itself is administered in three phases; remission induction, intensification, and maintenance phases. The prognosis depends upon the type of leukemia. Current treatment modalities predict only a 20-40% of survival rate among adults. The prognosis for children, however, is better.