Childhood acute lymphoblastic leukemia (ALL) is a type of Cancer in which the bone marrow makes too many lymphocytes (a type of white blood cell).

Childhood acute lymphoblastic leukemia (also called acute lymphocytic leukemia or ALL) is a cancer of the blood and bone marrow. This type of cancer usually gets worse quickly if it is not treated. It is the most common type of cancer in children.

Normally, the bone marrow produces stem cells (immature cells) that develop into mature blood cells. There are 3 types of mature blood cells:

• red blood cells that carry oxygen to all tissues of the body.
• white blood cells that fight infection and disease.
• Platelets that help prevent bleeding by causing blood clots to form.

In ALL, too many stem cells develop into a type of white blood cell called lymphocytes. These lymphocytes may also be called lymphoblasts or leukemic cells. There are 3 types of lymphocytes:

• B lymphocytes that make antibodies to help fight infection.
• T lymphocytes that help B lymphocytes make the antibodies that help fight infection.
• Natural killer cells that attack cancer cells and viruses.

In ALL, the lymphocytes are not able to fight infection very well. Also, as the number of lymphocytes increases in the blood and bone marrow, there is less room for healthy white blood cells, red blood cells, and platelets. This may lead to infection, anemia, and easy bleeding.

Exposure to radiation and family history may affect the risk of developing childhood ALL.

Possible risk factors for ALL include the following:

• Having a brother or sister with leukemia.
• Being white or Hispanic.
• Living in the United States.
• Being exposed to x-rays before birth.
• Being exposed to radiation.
• Past treatment with chemotherapy or other drugs that weaken the immune system.
• Having certain genetic disorders, such as Down syndrome.

Possible signs of childhood ALL include fever and bruising.

These and other symptoms may be caused by childhood ALL or by other conditions. A doctor should be consulted if any of the following problems occur:

• Fever.
• Easy bruising or bleeding.
• Petechiae (flat, pinpoint spots under the skin caused by bleeding).
• Bone or joint pain.
• Painless lumps in the neck, underarm, stomach, or groin.
• Pain or feeling of fullness below the ribs.
• Weakness or feeling tired.
• Loss of appetite.

Tests that examine the blood and bone marrow are used to detect (find) and diagnose childhood ALL.

The following tests and procedures may be used:

• Physical exam and history: An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patient's health habits and past illnesses and treatments will also be taken.
• Complete blood count(CBC) with differential: A procedure in which a sample of blood is drawn and checked for the following: The number of red blood cells and platelets. The number and type of white blood cells. The amount of hemoglobin (the protein that carries oxygen) in the red blood cells. The portion of the sample made up of red blood cells.
• Bone marrow aspiration and biopsy: The removal of a small piece of bone and bone marrow by inserting a needle into the hipbone or breastbone. A pathologist views the bone and bone marrow samples under a microscope to look for signs of cancer.
• Cytogenetic analysis: A test in which the cells in a sample of blood or bone marrow are looked at under a microscope to find out if there are certain changes in the chromosomes in the lymphocytes. For example, in ALL, part of one chromosome is moved to another chromosome. This is called the “Philadelphia chromosome.”
• Immunophenotyping: A test in which the cells in a sample of blood or bone marrow are looked at under a microscope to find out if malignant lymphocytes (cancer) began from the B lymphocytes or the T lymphocytes.
• Blood chemistry studies: A procedure in which a blood sample is checked to measure the amounts of certain substances released into the blood by organs and tissues in the body. An unusual (higher or lower than normal) amount of a substance can be a sign of disease in the organ or tissue that produces it.
• Chest x-ray: An x-ray of the organs and bones inside the chest. An x-ray is a type of energy beam that can go through the body and onto film, making a picture of areas inside the body.

Certain factors affect prognosis (chance of recovery) and treatment options.

The prognosis (chance of recovery) and treatment options depend on:

• Age and white blood cell count at diagnosis.
• How quickly and how low the white blood cell count drops after initial treatment.
• Gender and race.
• Whether the leukemia cells began from the B lymphocytes or the T lymphocytes.
• Whether there are certain changes in the chromosomes of lymphocytes.
• Whether the leukemia has spread to the brain and spinal cord.

Source: National Cancer Institute: cancer.gov