Understanding blood cancer

What is blood cancer?

Blood cancer is a type of cancer that affects the production and function of blood cells. Leukaemia is a type of blood cancer. Our bodies are made up of trillions of tiny building blocks called cells. And these cells make up every part of the body, including blood.  Most blood cancers begin in the bone marrow, the spongy material inside the bones and where new blood cells are produced. All blood cells begin as stem cells, which mature in the bone marrow. They then develop into the three types of blood cells: red blood cells, white blood cells, or platelets.

Blood cancer facts

  • Blood cancer is the 3rd biggest cancer killer and 5th most common cancer in the UK.
  • Every 16 minutes someone is diagnosed with blood cancer in the UK.
  • In the UK, approximately 250,000 people are currently living with blood cancer.
  • More than 35 people die every day from blood cancer in the UK.

How does blood cancer develop?

As part of normal processes, the body grows and repairs. Cells that make up our body are constantly dying and being replaced. Normally cells divide (one cell becomes two) in a very controlled way when new cells are needed to replace or repair. For example, in a healthy person, red blood cells only live in the blood for about 100-120 days, platelets live about 6 days and some white blood cells less than one day.
DNA is a substance found in most cells, which controls how cells develop, function and die. Changes can occur in the DNA that may result in the production of abnormal blood cells. These abnormal blood cells may be unable to mature or function properly. They represent a population of blood cells that do not die when they should or that divide too quickly. The abnormalities can lead to blood cancer.
In most blood cancers, the normal blood cell development process is disrupted by abnormal type or types of blood cell that continue to divide/multiply in an uncontrolled way. Not only do these abnormal blood cells not function properly, but they may also prevent the important normal function of blood, such as fighting infections or preventing serious bleeding.

There are three main types of blood cancer:


A type of cancer in blood or bone marrow which is caused by abnormal white blood cells (leukaemia cells). The leukaemia cells behave and function differently from normal blood cells. In leukaemia, a high number of abnormal white blood cells are not able to fight infection, and they may also impair the ability of the bone marrow to produce red blood cells and platelets.


A type of blood cancer that begins in the infection-fighting cells of the immune systems, called lymphocytes. Lymphocytes can be found in the lymph nodes, spleen, thymus, bone marrow and other parts of the body. Lymphoma occurs when abnormal lymphocytes become lymphoma cells, which multiply and collect in the lymph nodes and other tissues.


A type of cancer that forms in white blood cells called plasma cells. Plasma cells play an important role in the immune system by producing antibodies that recognise and fight infection-causing germs. In myeloma, abnormal myeloma cells accumulate in the bone marrow and crowd out normal healthy blood cells.

Other types include

A type of malignant blood disorder when the bone marrow doesn’t make enough healthy blood cells and instead makes abnormal cells that are unable to function normally.

A type of blood cancer that starts in the bone marrow. In MPN, the bone marrow makes too many of one or more types of blood cells (red blood cells, white blood cells and/or platelets).

Learn more about blood

Blood is essential to life. Blood circulates through the body and has many different functions, including: 

  • transporting oxygen and nutrients to the lungs and tissues 
  • forming blood clots to prevent excess blood loss  
  • carrying cells and antibodies that fight infection  

Blood consists of liquid and solid components. The liquid part, called plasma, consists of water, salts and protein. Over half of blood is plasma. The solid part of the blood contains red blood cells, white blood cells and platelets. 

Blood cell production

Blood cells are being made all the time, new blood cells to replace old ones that have worn out and died off. The new blood cells are made in the bone marrow and the process starts with a stem cell – an immature cell that can develop into all types of blood cells. In a healthy person, the system of blood cell production is finely controlled in a process called haematopoiesis.

Diagram showing the make up of blood including cells, plasma and platelets

Composition of blood

Red blood cells

Red blood cells (also known as erythrocytes) make up 40% to 45% of the volume of blood. They have a slightly indented flattened disk shape, often called a biconcave disc.

Red blood cells have an important function to transport oxygen to and from the lungs. The life span of a red blood cell is approx. 4 months, and they are regularly replaced. The human body produces around 2 million blood cells every second.

White blood cells

White blood cells (also known as leukocytes) make up approximately 1% of the volume of blood. Despite the low % they have a very important function. White blood cells are essential for good health and protection against illness and disease. White blood cells are constantly being generated in the bone marrow.

They flow through the bloodstream and attack foreign bodies, like viruses and bacteria. They can even leave the bloodstream to extend the fight into tissue. The number of white blood cells in a microliter of blood usually ranges from 3,700–10,500. Higher or lower levels of white blood cells can indicate disease.


Platelets are an amazing part of blood; they help blood to clot when there is a cut or wound. Platelets are the smallest of our blood cells and literally look like small plates in their non-active form. Platelets interact with clotting proteins to prevent or stop bleeding. Wherever a wound occurs, the blood vessel will send out a signal.

Platelets receive that signal, travel to the area and transform into their “active” formation, growing long tentacles. They make contact with the blood vessel to form clusters and plug the wound until it heals. There are usually between 150,000 and 400,000 platelets per microliter of human blood.


Plasma is the liquid portion of blood and makes up around 55% of the volume of blood.

Plasma is yellowish in colour and is mostly made up of water (92%), but it also contains proteins, sugars, hormones and salts. It transports water and nutrients to the body’s tissues.

How cells are made

When the stem cell divides, it can either produce more stem cells or other immature blast cells that develop into mature blood cells over time. In this process of specialisation, immature blast cells become either lymphoid or myeloid cells. 

Lymphoid cells are a type of white blood cell. They help fight infection, and they include B lymphocytes and T lymphocytes. 

Myeloid cells go on to form red blood cells, platelets and other types of white blood cells such as monocytes and granulocytes. 

Dr Miguel Ganuza, Queen Mary University of London and John Goldman Fellow 2020

Searching for answers – Leukaemia UK funded research

Dr Miguel Ganuza: 2020 John Goldman Fellow whose research is specifically interested in clonal haematopoesis (CH), where blood cells may accumulate with mutated DNA that are derived from one single mutated cell.

“My major aspiration is to contribute to the discovery of new treatments to prevent the development of different types of leukaemia.”

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