|Leukaemia is cancer of the blood and bone marrow (the soft material in the centre of most bones). Unlike other cancers, Leukaemia does not produce lump-like tumours but results in rampant overproduction of cancerous white blood cells. Leukaemia – the term derives from the Greek words for ‘white’ and ‘blood’ – is often considered a disease of children, yet it actually affects far more adults. It is more common in men than women. About 6,800 people get Leukaemia in the UK each year. About 2,700 of these are acute Leukaemia. The most common form is found more often in Caucasians.
Blood has three types of cells: white cells fight infection, red cells carry oxygen and platelets help to clot, all suspended in its liquid plasma. Every day, hundreds of billions of new blood cells are produced in the bone marrow – most of them red cells. In people with Leukaemia, however, the body starts producing more white cells than it needs. Many of the extra white cells do not mature normally, yet they tend to live well beyond their normal life span.
Despite their vast numbers, these leukemic cells are unable to fight infection the way normal white blood cells do. As they accumulate, they interfere with vital organ functions, including the production of healthy blood cells. Eventually the body does not have enough red cells to supply oxygen, enough platelets to ensure proper clotting, or enough normal white cells to fight infection, making people with Leukaemia, anaemic and susceptible to bruising, bleeding and infection.
Cases of Leukaemia are classified as acute or chronic. Cancer cells in acute Leukaemia start multiplying before they develop beyond their immature stage. Chronic Leukaemia progresses more slowly, with cancer cells developing to full maturity. Leukaemia is further classified according to the type of white blood cell involved. Under a microscope, two main types of white blood cells are easily distinguishable: Myeloid cells contain tiny particles or granules; lymphoid cells usually do not.
What are normal blood cells?
To understand how Leukaemia affects blood cells, it helps to know about normal blood cells.
All blood cells come from blood stem cells. Although some blood stem cells are in the blood, most are in the bone marrow. Blood stem cells produce three kinds of blood cells:
When blood cells become old or damaged, they die, and the blood stem cells produce new blood cells to take their place.
Normal Myeloid and Lymphoid Cells
The picture below shows that all blood cells are produced by blood stem cells. The picture shows two pathways. A blood stem cell can produce both myeloid stem cells and lymphoid stem cells:
All blood cells are produced by blood stem cells. The myeloid pathway leads to red blood cells, platelets, and white blood cells, and the lymphoid pathway leads to different types of white blood cells.
In a person with Leukaemia, the bone marrow produces abnormal white blood cells that are called Leukaemia cells and leukaemic blast cells. The abnormal cells can’t produce normal white blood cells.
Leukaemia cells divide to produce copies of themselves. The copies divide again and again, producing more and more Leukaemia cells.
Unlike normal blood cells, Leukaemia cells don’t die when they become old or damaged. Because they don’t die, Leukaemia cells can build up and crowd out normal blood cells. The low level of normal blood cells can make it harder for the body to get oxygen to the tissues, control bleeding, or fight infections.
Also, Leukaemia cells can spread to other organs, such as the lymph nodes, spleen, and brain.
Types of Leukaemia
Lab tests help the doctor find out the type of Leukaemia that you have. For each type of Leukaemia, the treatment plan is different.
Acute and Chronic Leukaemias
Leukaemias are named for how quickly the disease develops and gets worse:
Myeloid and Lymphoid Leukaemias
Leukemias are also named for the type of white blood cell that is affected:
Four Most Common Types of Leukaemia
Acute myeloid leukaemia (AML) affects myeloid cells and grows quickly. Leukemic blast cells collect in the bone marrow and blood.
Acute lymphoblastic leukaemia (ALL) affects lymphoid cells and grows quickly. Leukemic blast cells usually collect in the bone marrow and blood.
Chronic myeloid leukaemia (CML) affects myeloid cells and usually grows slowly at first. Blood tests show an increase in the number of white blood cells. The abnormal blood cells work okay. There may be a small number of leukemic blast cells in the bone marrow.
Chronic lymphocytic leukaemia (CLL) affects lymphoid cells and usually grows slowly. Blood tests show an increase in the number of white blood cells. The abnormal cells work almost as well as the normal white blood cells.