Blood cancer happens when something goes wrong with the development of your blood cells. This stops them working properly and they may grow out of control.

This can stop your blood doing the things it normally does to keep you healthy, like fighting off infections or helping repair your body.

Types of blood cancer

The main types of blood cancer are:

  • leukaemia,
  • lymphoma, and
  • myeloma.

There are also other blood cancers and related conditions that don’t fit within these groups such as myelodysplastic syndromes and myeloproliferative neoplasms.

Within these broad groups are many different blood cancers. Each specific type affects a particular type of blood cell and will have different symptoms, treatments and outlook (prognosis).

Acute and chronic blood cancers

You might see blood cancers described as either:

  • acute: this means an aggressive or fast-growing cancer that spreads quickly, or
  • chronic: this means a slower-growing or ‘indolent’ (lazy) cancer that takes longer to spread.

How does blood cancer start?

Cells are the tiny building blocks that our bodies are made of.  Every second of every day your body is refreshing your cells by making new ones and destroying old ones.

DNA is a substance within your cells.  It’s a kind of code that controls how cells develop, behave, and die. DNA is made up of small sections known as genes and packed into chromosomes in your cells.

If the DNA changes (mutates) in the stem cells that make your blood cells in your bone marrow, your blood cells might start to develop wrongly (abnormally), or fail to die when they should. These are the ‘cancerous’ or cancer cells.

The type of blood cancer you have generally depends on the type of blood cell that’s affected.

  • Leukaemia happens when your leukocytes (white blood cells) become cancerous.
  • Lymphoma happens when your lymphocytes (a certain type of white blood cell) become cancerous.
  • Myeloma happens when your plasma cells (a type of B lymphocyte) become cancerous.

What causes blood cancer?

All blood cancers are caused by faults in our DNA (mutations). In practically all cases these changes to our DNA happen for reasons we can’t explain and are linked to things we can’t control.

While in most cases we don’t know exactly what causes the changes to DNA that can lead to blood cancer, research has shown that there are a number of things that can affect how likely you are to develop certain types of blood cancer.

These ‘risk factors’ include:

  • age,
  • sex,
  • ethnicity,
  • family history,
  • radiation or chemical exposure, and
  • some health conditions and treatments.

The risk factors vary between the different types of blood cancer. For example, we know that myeloma only affects adults and is much more common in men and people from an African-Caribbean background, whereas Hodgkin lymphoma usually develops in people aged 15-25 or over 50, and people who already have problems with their immune system.

Blood counts

Everyone has slightly different numbers of each type of blood cell. If you’re healthy, the amount you have normally stays in the same range.

A ‘blood count’ is the term used to describe how many blood cells are in a sample of your blood.

What’s a normal blood count?

What’s considered a ‘normal’ blood range (blood count) can vary between different doctors, healthcare teams and hospitals, but as a general rule a healthy person is expected to have blood counts in the following ranges:

Type of blood cell Normal range for women Normal range for men
Red blood cells 3.8 to 5 x 1012/l 4.5 to 6.5 x 1012/l
Haemoglobin* 115g/l to 165 g/l 130g/l to 180 g/l
White blood cells 4 to 11 x 109/l 4 to 11 x 109/l
Neutrophils 2 to 7.5 x 109/l 2 to 7.5 x 109/l
Lymphocytes 1.3 to 4 x 109/l 1.3 to 4 x 109/l
Platelets 150 to 440 x 109/l 150 to 440 x 109/l

*Doctors are usually more interested in the concentration of your haemoglobin than the number of cells in your blood, so haemoglobin is measured slightly differently.