What is acute lymphoblastic leukaemia (ALL) ?

Acute lymphoblastic leukaemia (ALL) is a type of blood cancer. It starts from white blood cells called lymphocytes in the bone marrow. The bone marrow is the soft inner part of the bones, where new blood cells are made.

ALL usually develops quickly over days or weeks. It is the most common type of leukaemia to affect children but can also affect adults.

How common is ALL?

Acute lymphoblastic leukaemia is rare. Around 800 people are diagnosed with ALL in the UK each year.

ALL is most often diagnosed in children, teenagers and young adults. It is most common in young children aged 0 - 4 years. It is slightly more common in males than in females. 

What happens in ALL?

The word acute means that the leukaemia can develop quickly. This is because the lymphocytes are growing and dividing much quicker than usual. These abnormal cells build up in the bone marrow and spill out into the blood. 

 The leukaemia cells can spread into other parts of the body, including the:

  • lymph nodes Open a glossary item
  • liver
  • spleen Open a glossary item
  • central nervous system (brain and spinal cord)
  • testicles

The leukaemia cells can build up in the lymph nodes, liver and spleen and sometimes make them bigger. 

If it wasn't treated acute leukaemia would cause death within a few weeks or months. But treatments can work well for some people with ALL.

Blood cells and ALL

To understand how and why leukaemia affects you as it does, it helps to know how you make blood cells.

Your body makes blood cells in the bone marrow. The bone marrow is the soft inner part of your bones. You make blood cells in a controlled way, as your body needs them.

All blood cells start as the same type of cell, called a stem cell. This stem cell then develops into:

  • lymphoid stem cells, which become white blood cells called lymphocytes
  • myeloid stem cells, which become white blood cells called monocytes and neutrophils (granulocytes), red blood cells and platelets

The diagram helps explain this:


A simplified diagram showing how blood cells are made

In acute lymphoblastic leukaemia, the bone marrow makes too many B or T lymphocytes. These lymphocytes are not fully developed and are not able to work normally. They are often known as blast cells.

Diagram showing which cell ALL starts in

Types of leukaemia

There are several types and subtypes of leukaemia. The name of the leukaemia you have depends on:

  • how quickly it develops
  • the type of white blood cells it affects

Doctors divide leukaemia into two main groups, acute and chronic. Acute leukaemia develops very quickly. Chronic leukaemia tends to develop slowly, usually over months or years without causing many symptoms.

Doctors divide these groups further, depending on the type of white blood cell they affect.

In acute leukaemia:

  • acute myeloid leukaemia (AML) affects myeloid cells
  • acute lymphoblastic leukaemia (ALL) affects lymphoid cells

In chronic leukaemia:

  • chronic myeloid leukaemia (CML) affects myeloid cells
  • chronic lymphocytic leukaemia (CLL) affects lymphoid cells

How leukaemia can affect you

White blood cells help fight infection. If your body makes a lot of abnormal white blood cells, they can prevent normal healthy cells from developing. So you are more likely to get infections and may find it difficult to get rid of them.

Too many white blood cells can overcrowd the bone marrow. So there isn't enough space to make other types of blood cells. This can cause a lower than normal number of red blood cells and platelets.

Having too few red blood cells (called anaemia) makes you tired and breathless. You can have bleeding problems such as nosebleeds, if you don’t have enough platelets. 

Abnormal white blood cells can build up in parts of your body such as the spleen, lymph nodes and liver making them bigger. This can make your tummy (abdomen) swell and feel uncomfortable. The leukaemia cells can also spread to the brain. In men the testicles are sometimes affected, so let your doctor know if you have any swelling or pain in that area.

Unlike solid tumours, for example breast cancer, having leukaemia cells in different parts of your body doesn’t mean a worse outcome. 

Last reviewed: 
14 May 2021
Next review due: 
14 May 2024
  • Cancer Incidence from Cancer Intelligence Statistical Information Team at Cancer Research UK  (2015 - 2017 UK average) 
    Accessed May 2021

  • Hoffbrand’s Essential Haematology (8th Edition)
    AV Hoffbrand and D A Steensma
    Wiley Blackwell, 2020

  • Cancer: Principles and Practice of Oncology (11th edition)
    V T De Vita, T S Lawrence and S A Rosenberg
    Wolters Kluwer, 2019

  • Suspected cancer: recognition and referral
    National Institute for Health and Care Excellence (NICE), June 2015. Last Updated January 2021

  • Acute lymphoblastic leukaemia
    F Malard and M Mohty
    The Lancet, 2020. Volume 395, Issue 10230, Pages 1146 to 1162

  • The information on this page is based on literature searches and specialist checking. We used many references and there are too many to list here. Please contact patientinformation@cancer.org.uk with details of the particular issue you are interested in if you need additional references for this information.

Related links