Most people think that leukaemia is a form of cancer of the blood. This is not strictly true…
Leukaemia is really a cancer of the bone marrow. The bone marrow is found in the marrow cavities of the long bones, ribcage and pelvis and contains many different types of cells which actually produce all the various types of blood cells.
The bone marrow is the blood-making factory of the body producing hundreds of millions of red and white blood cells each and every day of our lives. If one of these bone marrow cells becomes cancerous it starts to grow and divide aggressively, out of all control, and pushes out all the normal blood making cells from the bone marrow. Consequently normal blood production ceases and the bone marrow and blood begin to fill up with cancerous leukaemia cells, which serve no useful function.
There are many different types of bone marrow cell which give rise to the various types of blood cells, and it is the particular type of bone marrow cell which becomes malignant that determines the type of leukaemia that develops.
Broadly speaking there are two main categories of leukaemia…
Acute, which starts suddenly and progresses rapidly killing the patient in a matter of weeks if left untreated, and…
Chronic, which starts gradually and progresses slowly, sometimes taking many months or even years to kill the patient.
Acute leukaemia can be divided into two main types…
Acute lymphoblastic leukaemia (ALL) which affects mainly children but only relatively few adults / Acute myeloid leukaemia (AML) which affects mainly adults but relatively few children.
Chronic leukaemia similarly exists as two main types…
Chronic lymphocytic leukaemia (CLL) which effects mainly elderly men / Chronic myeloid leukaemia (CML) which usually affects young or middle aged men and women.
Each of these main forms of leukaemia can be further subdivided into different subgroups, a description of which lies outside the scope of this section.
Identifying the type of leukaemia a patient has is important, because the different types of leukaemia require different treatments, and the prognosis for the patient also differs markedly depending upon the type of leukaemia.
How does leukaemia affect the patient?
Generally patients become weak and tired and appear pale, primarily because they are anaemic due to a deficiency of red blood cells.
They often develop fevers due to infections (because of an insufficiency of certain types of white blood cells which normally defend us against infections), and bruise or bleed easily due to a lack of special particles in the blood called platelets, which normally help blood to clot.
All of these signs and symptoms are due to the failure of the bone marrow in producing normal blood cells due to the fact that the useless leukaemia cells have replaced all the normal bone marrow cells.
If the patient is not treated urgently they will die from overwhelming infections, anaemia or bleeding.
The patient usually goes to see a doctor because of one or all of the above symptoms. If the doctor is suspicious that the patient has leukaemia he will arrange for the patient to have a simple blood test. This will reveal whether there are any leukaemia cells in the blood or alternatively will show there to be an excess or deficiency in normal blood cells.
If this is shown to be the case then the patient will be asked to have a bone marrow biopsy. This is where a small sample of bone marrow is removed with a needle and syringe, usually from the pelvis, and is inspected under the microscope by a specialist called a haematologist.
This will reveal whether normal bone marrow cells have been replaced by leukaemia cells and is the definitive test upon which the diagnosis can be made.The haematologist also has a series of special tests that can be used on the bone marrow cells to establish the particular type of leukaemia the patient has.