What is acute lymphoblastic leukaemia | Cancer Research UK
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What is acute lymphoblastic leukaemia

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Acute lymphoblastic leukaemia (ALL) is a type of blood cancer that starts from young 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. It usually develops quickly over days or weeks. It is the most common type of leukaemia to affect children but can also affect adults.

 

A quick guide to what's on this page

The blood and acute lymphoblastic leukaemia

Leukaemia is a cancer of the white blood cells and bone marrow. There are several types and subtypes. Acute lymphoblastic leukaemia (ALL) affects white blood cells called lymphocytes.  It usually develops quickly over days or weeks. It is the most common type of leukaemia to affect children but can also affect adults.

Blood cells and leukaemia

Your body makes blood cells in the bone marrow. This 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. Stem cells then develop into one of four different types, which in turn become red blood cells, platelets, or different types of white blood cells.

In acute lymphoblastic leukaemia, the bone marrow makes too many immature white cells called lymphoblasts. These lymphoblasts are not fully developed and are not able to work normally.

How leukaemia affects you

White blood cells help fight infection. If your body makes abnormal white blood cells, you are more likely to get infections. You can find it difficult to get rid of the infections. 

If there are too many white blood cells, the bone marrow gets overcrowded and there is not enough space for other types of blood cells. So you may have a lower than normal count of red blood cells and platelets. Abnormal white blood cells can also build up in parts of the lymphatic system (the spleen and lymph nodes) and in the liver.
 

CR PDF Icon You can view and print the quick guides for all the pages in the about ALL section.

 

 

What happens in ALL

The word acute means that the leukaemia can develop quickly, and if not treated, would probably cause death within a few months. But treatments these days work very well. The bone marrow produces white blood cells called lymphocytes too quickly because they grow and divide too fast. These abnormal cells build up in the blood. The leukaemic cells can eventually spread into other parts of the body, including the lymph nodes, liver, spleen, central nervous system (brain and spinal cord), and testicles (in males).

The cells can build up in the lymph nodes, bone marrow and spleen and cause swelling. 

 

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

  • Myeloid stem cells – which become white blood cells called monocytes and neutrophils (a type of granulocyte)
  • Lymphoid stem cells – which become white blood cells called lymphocytes
  • Erythroblasts – which become red blood cells
  • Megakaryocytes – which become platelets

The diagram below helps to explain this.

Diagram showing how blood cells are made

In acute lymphoblastic leukaemia, the bone marrow makes too many lymphocytes. These lymphocytes are not fully developed and are not able to work normally.

Diagram showing which cell ALL starts in

 

How leukaemia affects you

White blood cells help fight infection. But if your body makes abnormal white blood cells, they don’t work properly. So you are more likely to get infections and find it difficult to get rid of them.

Too many white blood cells can overcrowd the bone marrow. So, there isn't enough space for other types of blood cells. Then you might have a lower than normal number of red blood cells and platelets.

Having too few red blood cells makes you tired and breathless (anaemic). And if you don’t have enough platelets, you can have bleeding problems (for example, nosebleeds).

Abnormal white blood cells can build up in parts of the lymphatic system, such as the spleen and lymph nodes, making them swell. They might build up in the liver. This can make your tummy (abdomen) swell and feel uncomfortable. The leukaemia cells can also spread to the brain, and the testicles in men.

Read more about the symptoms of acute lymphoblastic leukaemia.

 

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 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

These pages are about acute lymphoblastic leukaemia (ALL). 

You can read about other types of leukaemia.

 

The difference between ALL and lymphoma

Lymphomas are another type of cancer that can develop from the white blood cells called lymphocytes. The main difference is that ALL starts in the bone marrow and may spread to other parts of the body. But lymphomas start in the lymph nodes and other organs, and then may spread into the bone marrow.

If you have cancerous lymphocytes in both your bone marrow and lymphatic system, it can sometimes be difficult to tell whether you have ALL or lymphoma. Your tests help your doctor to diagnose which it is. You can find more information about non Hodgkin’s lymphoma and Hodgkin’s lymphoma in the sections on different types of cancer.

Children's impact statement - Leukaemia

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Updated: 5 May 2016