Types of Leukemia in Children

Bone marrow is the tissue within bones that produces the body’s blood cells. These cells include healthy white blood cells that prevent infection, red blood cells that carry oxygen to the organs, and platelets that help the blood to clot. In childhood leukemia, the bone marrow produces abnormal white blood cells that crowd out healthy blood cells, preventing them from doing their job of fighting infection.

Children with leukemia typically have one of three main types: acute lymphoblastic leukemia, acute myeloid leukemia, or chronic myelogenous leukemia. Our specialists diagnose the specific type of leukemia based on the type of white blood cells present in the child’s blood, bone marrow, or both; whether the leukemia is chronic or acute; and the chromosomal and genetic makeup of these cancer cells.

During diagnosis, your child’s doctors determine the severity of the leukemia by considering several factors, including the child’s age; the type and amount of white blood cells in the blood; symptoms; changes in certain chromosomes in the leukemia cells; and whether the cancer has spread to other areas of the body, including the spinal fluid.

Based on this information, the doctors categorize the cancer. These categories, or risk groups, usually apply to acute cancers and indicate the severity of the condition. They also help the doctor determine which treatment may be most effective. The risk group is usually reassessed after the first month of treatment as the leukemia begins to respond.

Acute Lymphoblastic Leukemia

Approximately 80 percent of childhood leukemias are classified as acute lymphoblastic leukemia, commonly known as ALL. In children with this condition, the bone marrow creates too many lymphoblasts, a type of immature white blood cell. These abnormal cells crowd out healthy white blood cells, which can lead to anemia, a tendency to bleed, and decreased ability to fight infection.

Acute lymphoblastic leukemia is divided into two subtypes that are based on the type of white blood cells present at diagnosis—B cell or T cell. Most acute lymphoblastic leukemias—about 85 percent—are B-cell leukemia. Risk groups for acute lymphoblastic leukemia are initially described as being “standard” or “high” and affect the type of treatment that may be most effective. Children with a high risk group require additional therapy.

Acute Myeloid Leukemia

Childhood acute myeloid leukemia, commonly known as AML, is a cancer of the blood and bone marrow that begins in immature white blood cells called myeloblasts that are located within bone marrow. Myeloblasts normally grow to become one of three types of mature blood cells: red or white blood cells or platelets.

However, in people who have this type of leukemia, cancerous myeloblast cells divide quickly, eliminating healthy blood cells and platelet-producing cells from the body’s bone marrow, which eventually stops working correctly. This type of cancer accounts for close to 15 to 20 percent of childhood leukemias. There are eight subtypes of acute myeloid leukemia, and they are based on the type and maturity of the white blood cells.

Chronic Myelogenous Leukemia

Chronic leukemias are rare in children. Chronic myelogenous leukemia, commonly known as CML, is a cancer of the bone marrow that accounts for just 2 percent of all childhood leukemias. Most children with chronic myelogenous leukemia have an abnormal gene called BCR-ABL in the cancer cells that’s created by a translocation, or switching, of chromosomes. This gene, which is also referred to as the Philadelphia chromosome, causes the body to make too many white blood cells, which crowd out healthy cells and increase a child’s chances of infection.

Chronic myelogenous leukemia can be further staged by the number of immature or blast cells circulating in the blood, and is classified into three phases: chronic, accelerated, and blastic. Left untreated, chronic myelogenous leukemia can transform into a faster-growing, blastic acute leukemia that is much more difficult to treat.