Facts & Resources

Understanding Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia (ALL) is one type of cancer of the bone marrow and blood. ALL is also called acute lymphocytic leukemia and acute lymphoid leukemia. Fred Hutch offers comprehensive treatment from a team of experts for every type of leukemia, including ALL.

In people with ALL, something goes wrong with a type of blood stem cell called a lymphoblast. 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 do their normal infection-fighting functions. They build up in your bone marrow and blood, crowding out the 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 keep your organs from working right. ALL gets worse quickly if it is not treated, which makes it important to start treatment soon after diagnosis.

What Causes ALL?

We do not know what causes ALL. The disease is more common in children aged 5 or younger, and the risk is also higher after age 50. It is more common in males than females, and it is more common in white people than Black people.

There are a few risk factors we know about:

  • 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 U.S.
  • Having certain genetic conditions, such as Down syndrome
  • Having an identical twin who develops ALL as an infant or young child

However, keep in mind that many people who develop ALL do not have any of these risk factors, and most people with these risk factors do not develop the disease.

Classifying ALL

Most cancers are given a numbered stage based on the size of the tumor and how far the disease has spread. Because leukemia often doesn’t form a solid tumor and it is found throughout the body, there is no official 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 (the disease got better but then got worse). 
  • Refractory ALL. This means the leukemia has not responded to treatment.

Subtypes of Acute Lymphoblastic Leukemia

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 
  • If the cells have chromosomal abnormalities (mutations)

Most people with ALL (about 80 percent) have a B-cell subtype. Some subtypes have an unusual number of chromosomes. In other subtypes, two chromosomes exchange DNA, which is called a translocation.

B-cell ALL

B-cell ALL starts in immature cells that would otherwise develop into B-cell lymphocytes, a part of our immune system that (among other things) makes antibodies. B-cell is the most common subtype of ALL.

T-cell Lymphoma

T cells are a type of white blood cell and part of the immune system. Like the B-cell subtype, T-cell ALL starts in immature cells. It’s a less common subtype that happens more often in adults than children. Among adults, this subtype is about 25 percent of cases. 

Mixed Phenotype Acute Leukemia

Mixed phenotype acute leukemia is a very rare subtype that is only about 2–5 percent of cases. It is diagnosed when someone has more than one type of leukemia at the same time or if their cancer cells have features of more than one type: both acute lymphoblastic leukemia and acute myeloid leukemia (AML). 

Philadelphia chromosome-positive ALL (Ph+ ALL)

About 25 percent of adult ALL patients have this subtype. The Philadelphia chromosome is the most common translocation (when two chromosomes exchange DNA) in adult ALL. This means parts of chromosomes 9 and 22 get rearranged. Two genes called BCR and ABL join together in chromosome 22 to make one gene called BCR-ABL. Because this subtype is caused by the Philadelphia chromosome, it is called Philadelphia chromosome-positive ALL (Ph+ ALL). ALL. Instead, ALL is classified as:

Types of Treatment for ALL

Today, there are more treatment options than ever before to put ALL into remission. Your care team will make sure you understand each type of treatment and all your choices.

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 are able 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 make 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 the blood that circulates in your body. Blood stem cells make lymphoid stem cells and myeloid stem cells.

  • Lymphoid stem cells make lymphoblasts. Lymphoblasts make several types of white blood cells.
  • Myeloid stem cells make myeloblasts. Myeloblasts make white blood cells, red blood cells and platelets.

What do healthy blood cells do?

Healthy white blood cells, red blood cells and platelets are very important.

  • 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 get rid of it (by breathing it out).
  • Platelets make your blood clot and slow or stop bleeding.
blood cells

Fred Hutch has researched and treated of ALL for decades.


There are many resources online for learning about your disease. Health educators at the Fred Hutch Patient and Family Resource Center have compiled a list of trusted sources to help you get started.

Whether you are newly diagnosed, going through treatment or know someone with cancer, our staff are available to tailor personalized resources and answer questions about support options in the community. 

Cancer Research Organizations

Our list of online resources provides accurate health information from reliable and reputable sources, like the National Cancer Institute (NCI), the American Society of Clinical Oncology (ASCO) and the National Comprehensive Cancer Network (NCCN).

American Cancer Society

American Cancer Society (ACS): Overview of Acute Lymphoblastic Leukemia

If you have acute lymphocytic leukemia (ALL) or are a caregiver for someone who does, knowing what to expect can be helpful. Here you can find out all about ALL in adults, including risk factors, symptoms and how they are found and treated.

American Society of Clinical Oncology

American Society of Clinical Oncology (ASCO): Guide to Acute Lymphocytic Leukemia

This is Cancer.Net's Guide to ALL. Here you can learn more about ALL, treatment, the latest research and clinical trials.

Leukemia & Lymphoma Society

Leukemia & Lymphoma Society (LLS): Overview of Acute Lymphoblastic Leukemia

If you have ALL, LLS is a good place to start to better understand your diagnosis, treatment and support options.

National Comprehensive Cancer Network

National Comprehensive Cancer Network (NCCN) Guidelines for Patients: Acute Lymphocytic Leukemia

This step-by-step guide to the latest advances in cancer care features questions to ask your physician, patient-friendly illustrations and glossaries of terms and acronyms.


CancerCare: Blood Cancers Support Group

CancerCare offers an online blood cancers support group.

Cancer Support Organizations

Our list includes local and national organizations that are dedicated to improving the quality of life for patients and family members through providing emotional support, education and community.



CancerCare: Blood Cancers Support Group

CancerCare offers an online blood cancers support group.