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General Information About Childhood Acute Lymphoblastic Leukemia


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 makes blood stem cells (immature cells) that develop into mature blood cells over time. A blood stem cell may become a myeloid stem cell or a lymphoid stem cell.

The myeloid stem cell develops into one of three types of mature blood cells:

  • Red blood cells that carry oxygen and other materials to all tissues of the body.
  • Platelets that help prevent bleeding by causing blood clots to form.
  • Granulocytes (white blood cells) that fight infection and disease.

The lymphoid stem cell develops into a lymphoblast cell and then into one of three types of lymphocytes (white blood cells):

  • 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.
     
Photo by Cancer Type

Blood cell development. A blood stem cell goes through several steps to become a red blood cell, platelet, or white blood cell.
 

In ALL, too many stem cells develop into lymphoblasts or lymphocytes. These cells may also be called leukemic cells. The leukemic cells 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.

There are subgroups of childhood ALL.

Four of the subgroups of ALL are based on the type of blood cell that is affected, whether there are certain changes in the chromosomes, and age at diagnosis:

  • T cell ALL.
  • Philadelphia chromosome positive ALL.
  • ALL diagnosed in an infant.
  • ALL diagnosed in children who are aged 10 and older and adolescents (teenagers).

These subgroups are treated differently from other types of ALL.

Family history and exposure to radiation may affect the risk of developing childhood ALL.

Anything that increases your risk of getting a disease is called a risk factor. Having a risk factor does not mean that you will get cancer; not having risk factors doesn’t mean that you will not get cancer. People who think they may be at risk should discuss this with their doctor. 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. Other conditions may cause the same symptoms. 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 bone marrow, blood, and a small piece of bone by inserting a hollow needle into the hipbone or breastbone. A pathologist views the bone marrow, blood, and bone under a microscope to look for signs of cancer.
     
  • Cytogenetic analysis: A laboratory test in which the cells in a sample of blood or bone marrow are viewed under a microscope to look for 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.”
     
Photo by Cancer Type

Philadelphia chromosome. A piece of chromosome 9 and a piece of chromosome 22 break off and trade places. The bcr-abl gene is formed on chromosome 22 where the piece of chromosome 9 attaches. The changed chromosome 22 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 makes 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 leukemia 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.
  • Whether the child has Down syndrome.

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Source: National Cancer Institute, www.cancer.gov