Leukaemia is a cancer of the white blood cells. All blood cells are made in the bone marrow, the spongy substance at the core of some bones in the body.
Bone marrow contains:
- red blood cells, which carry oxygen around the body
- platelets, which help the blood to clot and control bleeding
- white blood cells, which help fight infection.
There are two different types of white blood cells; lymphocytes and myeloid cells (including neutrophils). These white blood cells work together to fight infection. Normally, white blood cells develop, repair and reproduce themselves in an orderly and controlled way. In leukaemia, however, the process gets out of control and the cells continue to divide in the bone marrow, but do not mature.
These immature dividing cells fill up the bone marrow and stop it from making healthy blood cells. As the leukaemia cells are not mature, they cannot work properly. This leads to an increased risk of infection.
There are four main types of leukaemia:
Chronic leukaemias usually affect adults and each type of leukaemia has its own characteristics and treatment. ALL is a cancer of immature lymphocytes, called lymphoblasts or blast cells.
There are two different types of lymphocytes; T-cells and B-cells. Often, leukaemia occurs at a very early stage in the immature lymphocytes, before they have developed into either T-cells or B cells. However, if the cells have developed this far before becoming leukaemic, the type of leukaemia may be known as T-cell or B-cell leukaemia.
This factsheet is about acute lymphoblastic leukemia (ALL).