Leukaemia (also spelled leukemia) is cancer that affects the blood and bone marrow. It happens when the bone marrow makes too many white blood cells (lymphocytes). Lymphocytes are part of the body’s immune system, which helps fight infections.
If you have leukaemia, your white blood cells don’t work properly. Leukaemia cells don’t fight infections very well. They can also take up a lot of space in the bone marrow. This means there is less room for healthy blood cells.
Types of leukaemia are named after:
- the type of stem cells involved
- how fast the cancer cells grow
Leukaemia affects two main stem cell types: lymphoid stem cells and myeloid stem cells. Most childhood leukaemias are acute, which means the cancer cells grow quickly.
Acute lymphocytic leukaemia (ALL)
Acute lymphocytic leukaemia (ALL) is also known as acute lymphoblastic leukaemia. ALL is the most common type of leukaemia in children. About seven to eight out of 10 children with leukaemia have ALL.1 Most children with ALL are between two and four years old.
ALL affects lymphoid stem cells and grows quickly.
Acute myeloid leukaemia (AML)
Acute myeloid leukaemia (AML) makes up most of the other childhood leukaemias. AML affects myeloid stem cells and grows quickly. You might also hear it called:
- acute myelogenous leukaemia
- acute myeloblastic leukaemia
- acute granulocytic leukaemia
- acute nonlymphocytic leukaemia
You might have heard of other types of leukaemia. These are rare in children under the age of 14:
- chronic lymphocytic leukaemia (CLL)
- chronic myeloid leukaemia (CML)
You might also have heard of ‘mixed lineage leukaemias’. These leukaemias are a combination of AML and ALL. These are usually treated like ALL.2
 https://www.cancer.org/cancer/leukemia-in-children/about/what-is-childhood-leukemia.html, https://www.childrenwithcancer.org.uk/childhood-cancer-info/cancer-types/acute-lymphoblastic-leukaemia/