About Acute Lymphoblastic Leukemia (ALL)

Some 3,800 new cases of acute lymphoblastic leukemia are diagnosed in the United States every year. Of this number, 2,400 cases are children. ALL accounts for 75 percent of childhood leukemia cases. Peak incidence rates are between the ages of one and five, although the disease can develop at any age.

ALL is characterized by the accumulation of immature lymphocytes, or blasts, in the blood stream and bone marrow. In healthy people, these early lymphocytes develop into mature white blood cells. Abnormal lymphocytes do not mature, and are often larger than normal. The rapid reproduction of abnormal lymphocytes results in high white blood cell counts and low levels of red blood cells.

Excessively high white blood cell counts may indicate the presence of ALL. Blood tests and bone marrow biopsies reveal the presence of blasts in both the bloodstream and bone marrow tissue.

ALL is also associated with certain chromosomal translocations, where genetic information on one chromosome swaps places with information on another chromosome.

Acute lymphoblastic leukemia has three subtypes. L1 lymphocytes are small, and very few structural differences appear among the abnormal lymphocytes. L2 has larger lymphocytes, and their shapes are more varied. L3 has large, varied lymphocytes like L2, but they are filled with bubble-like features called vacuoles.

Further classification is achieved by determining the abnormal lymphoctyes' immunophenotype, the surface markers of the leukemia cells. In 85 percent of ALL cases, the markers resemble those of healthy B lymphocytes, while the remaining fifteen percent resemble T lymphocytes. The distinction helps determine appropriate treatments.

The overall prognosis for ALL is very positive: eighty percent of children who have it are cured of the disease. Children between the ages of one and ten are most likely to be cured.

Subtype L3 has a less positive prognosis than subtypes L1 and L2. Other negative factors include high white blood cell counts and remission that takes longer than four weeks. The presence of chromosomal translocations also has a negative impact on the prognosis.

The subtypes include:

Each subtype is further classified according to its resemblance to B or T cells.

Resources

American Cancer Society. (updated 2003). What are the key statistics for adult acute leukemia?

American Cancer Society. (updated 2004). What is acute leukemia?

Beers, M. H., & Berkow, R., (ed). Leukemia. The Merck Manual of Diagnosis and Therapy, 17th Edition. Merck Research Laboratories, NJ, 1999.

Fauci, A., Braunwald, E., Isselbacher, K., Wilson, J., Martin, J., Kasper, D., Hauser, S., & Longo, D. (ed). (1998). Harrison's Principles of Internal Medicine, 14th Edition. McGraw-Hill, NY, 1998.

Leukemia and Lymphoma Society. (updated 2002). Acute lymphocytic leukemia.

Mittal, P., & Meeham, K. (2001). The acute leukemias. Hospital Review.

Smith, M., Ries, L., Gurney, J., & Ross, J. (nd). Leukemia. National Cancer Institute.