Acute lymphoblastic leukemia (ALL) is one type of cancer of the bone marrow and blood. It is also called acute lymphocytic leukemia or acute lymphoid leukemia.
Seattle Cancer Care Alliance (SCCA) offers comprehensive treatment from a team of experts for all types of leukemia, including ALL.
What is acute lymphoblastic leukemia?
In people with ALL, a type of blood stem cell called a lymphoblast begins to function abnormally.
- Instead of maturing into fully functioning lymphocytes — important immune-system cells — the lymphoblasts multiply out of control, and they don’t die off like normal blood cells do.
- The underdeveloped (leukemic) cells can’t carry out their normal infection-fighting functions.
- They build up in your bone marrow and blood, crowding out normal, healthy blood cells that your body needs.
- Low levels of normal blood cells can lead to infection, anemia and excessive bleeding.
- The leukemic cells can travel around your body through your bloodstream and interfere with the function of your organs.
ALL gets worse quickly if it is left untreated, which makes it important to start treatment soon after diagnosis.
Understanding your bone marrow and blood
To understand leukemia, it helps to know the basics about your bone marrow and blood cells.
What are stem cells?
Stem cells are cells in your body that have the potential to turn into any kind of cell, such as a skin cell, liver cell, brain cell or blood cell. Stem cells that turn into blood cells are called hematopoietic stem cells, or blood stem cells.
Why are blood stem cells important?
When blood cells become old or damaged, they die, and blood stem cells produce new blood cells to replace them. Blood stem cells are mainly found in bone marrow (the soft, spongy tissue inside your bones), but some are also found in circulating blood.
Blood stem cells produce lymphoid stem cells and myeloid stem cells.
- Lymphoid stem cells produce lymphoblasts, which in turn produce several types of white blood cells.
- Myeloid stem cells produce myeloblasts, which in turn produce white blood cells, red blood cells and platelets.
What do healthy blood cells do?
Healthy white blood cells, red blood cells and platelets are essential.
- White blood cells fight infection. The main types of white blood cells are B lymphocytes (B cells), T lymphocytes (T cells), natural killer (NK) cells and granulocytes.
- Red blood cells carry oxygen from your lungs to other parts of your body and take carbon dioxide back to your lungs to be removed.
- Platelets make your blood clot and slow or stop bleeding.
Symptoms of ALL
Many of the early symptoms of ALL are similar to the flu or other common, less serious diseases. Check with your doctor if you have any of these.
Symptoms from low white blood cells:
- Flu-like symptoms, such as fever, sweats and body aches
- Mouth inflammation, pain or sores
Symptoms from low red blood cells:
- Shortness of breath
- Pale skin
- Fatigue, weakness, lack of energy or sleepiness
Symptoms from low platelets:
- Bleeding from your gums
- Red spots on your palate or ankles
- Easy bruising or prolonged bleeding from cuts
- Frequent or severe nosebleeds
Other general symptoms:
- Loss of appetite
- Unexplained weight loss
- Pain or aches in your bones, stomach, arms, legs or back
- Swollen abdomen
- Swollen lymph nodes in your neck, underarm, stomach or groin
If your doctor suspects you may have leukemia, they will want to perform a thorough physical examination and talk with you about your medical history.
An accurate diagnosis of ALL requires several tests. You might have any or all of these.
- Blood tests — to check the types and numbers of blood cells, check the amount of hemoglobin (protein that carries oxygen) and look for lymphoblasts (complete blood count and peripheral blood smear) and to see if leukemic cells are present and which type they are (immunophenotyping, or flow cytometry).
- Bone marrow tests — taking samples of bone marrow and a small piece of bone from your pelvis using a needle (bone marrow aspiration and biopsy) and checking them for leukemic cells.
- Chromosome test — checking your blood or bone marrow cells for changes in chromosomes, such as an abnormal number of chromosomes or two chromosomes that have exchanged some DNA. These tests include cytogenetic analysis, fluorescent in situ hybridization and polymerase chain reaction.
- Lumbar puncture — taking a sample of cerebrospinal fluid from your spine with a needle to check whether leukemia has spread to your spinal cord and brain.
- Imaging tests — such as chest X-ray, computed tomography (CT) scan, magnetic resonance imaging (MRI) scan or ultrasound to check whether leukemia is impacting other parts of your body.
Subtypes of ALL
To help plan your treatment, your team will use your test results to tell which subtype of ALL you have. ALL is divided into subtypes based on:
- Which type of lymphocyte the leukemic cells come from (B cells or T cells)
- How mature the leukemic cells are
- Whether the cells have chromosomal abnormalities
Most people with ALL (about 80 percent) have a B-cell subtype.
Some subtypes have an abnormal number of chromosomes. In other subtypes, two chromosomes exchange DNA in what is called a translocation.
The most common translocation in adult ALL results in the Philadelphia chromosome. This means parts of chromosomes 9 and 22 rearranged. Two genes called BCR and ABL fuse together in chromosome 22 to make one gene called BCR-ABL. About 25 percent of adult ALL patients have this subtype, called Philadelphia chromosome–positive ALL (PH+ ALL).
Most cancers are assigned a numbered stage based on the size of the tumor and how far the disease has spread. Typically, leukemia doesn’t form a solid tumor and it is found throughout the body, so there is no formal staging system for ALL.
Instead, ALL is classified as:
- Newly diagnosed ALL, or untreated ALL. Treatment may have begun for relief of symptoms, such as fever and bleeding, but treatment has not begun for the leukemia.
- ALL in remission. After treatment, you may be considered in remission if your complete blood count is normal, there are no leukemia cells in your bone marrow and you have no signs or symptoms of leukemia.
- Relapsed ALL, or recurrent ALL. This means your leukemia returned after going into remission.
- Refractory ALL. This means the leukemia has not responded to treatment.
How common is ALL?
About 6,000 people are diagnosed with ALL each year in the U.S. While ALL is the most common type of leukemia in children, it is the least common type in adults. Only one-quarter of ALL cases are diagnosed in people age 20 or older.
What causes ALL?
Doctors do not know what causes ALL. The disease is more common in children age 5 or younger, and the risk increases again after age 50. It is also more common in males than females and in whites than African-Americans.
The few known risk factors include:
- Being exposed to high levels of radiation
- Being exposed to certain chemicals, such as chemotherapy or benzene
- Having certain viral infections, although this is more common outside the United States
- Having certain genetic conditions, such as Down syndrome
- Having an identical twin who develops ALL as an infant or young child
Keep in mind that many people who develop ALL have none of these risk factors, and most people with these risk factors do not develop the disease.