Hodgkin lymphoma

Hodgkin lymphoma is a blood cancer that begins in the white blood cells called lymphocytes. It is one of the two main groups of lymphoma. The other group is non-Hodgkin lymphoma.

Hodgkin lymphoma is sometimes called Hodgkin’s disease. The name Hodgkin comes from the doctor who first described this cancer. The disease usually starts in a lymph node at one or more places in the body, and is often first noticed in the neck. It can spread through the lymphatic system from one group of lymph nodes to another, and to other lymph tissue, particularly the spleen and bone marrow. Sometimes Hodgkin lymphoma appears in several parts of the body at the same time.

Occasionally, Hodgkin lymphoma spreads outside the lymphatic system to form a tumour in other organs, such as the liver or lung. This is known as extranodal disease.

Learn more about:

• What is blood cancer?
• The lymphatic system
• The role of blood cells
• Types of Hodgkin lymphoma
• What causes Hodgkin lymphoma?
• Who gets Hodgkin lymphoma?
• What is non-Hodgkin lymphoma?

What is blood cancer?

Cancer is a disease of the cells, and cells are the body’s basic building blocks – they make up tissues and organs. The body constantly makes new cells to help us grow, replace worn-out tissue and heal injuries. Normally, cells multiply and die in an orderly way, so that each new cell replaces one lost. Cancer develops when cells become abnormal and keep growing. When a cancer begins in abnormal blood cells, it is known as a blood cancer.

The three main groups of blood cancers are lymphoma, leukaemia and myeloma. Lymphoma is cancer of the body’s lymphatic system. In lymphoma, abnormal white blood cells called lymphocytes grow and multiply uncontrollably and can form a lump (tumour), usually in a lymph node. If these abnormal lymphocytes continue to build up, they can spread through the lymph vessels to form a tumour in another part of the lymphatic system. Occasionally, lymphoma travels through the bloodstream to form a tumour in an organ outside the lymphatic system, such as the liver or lung.

As the abnormal lymphocytes replace normal cells, the body’s immune system often becomes less able to resist and fight infections.

Sometimes other types of cancer spread to the lymph nodes. This is not lymphoma. For example, breast cancer that spreads to the lymph nodes is still called breast cancer.

How lymphoma starts and spreads

The lymphatic system

Hodgkin lymphoma is a cancer of the lymphatic system. The lymphatic system is part of the immune system, which protects the body against disease and infection. It is made up of a network of vessels, tissues and organs:

Lymph vessels – These thin tubes are found throughout the body and in organs such as the spleen, liver, thymus gland and bone marrow. Lymph vessels carry lymph fluid around the body.

Lymph fluid – This clear fluid travels to and from the tissues in the body, carrying nutrients and taking away bacteria, viruses, abnormal cells and cell debris.

Lymph nodes – Also called lymph glands, these small, bean-shaped structures are made up of lymph tissue. There are about 600 lymph nodes found in groups along the lymph vessels, including in the neck, underarms, chest, abdomen and groin. The lymph nodes filter lymph fluid as it passes through the body, before emptying most of the fluid into the bloodstream.

Other lymph tissue – As well as lymph nodes, lymph tissue is found in other parts of the body:

• bone marrow – produces blood cells
• thymus gland – helps produce white blood cells
• spleen – stores white blood cells, filters waste products from the blood, and destroys old blood cells, abnormal cells and bacteria
• tonsils – trap inhaled or ingested germs
• some lymph tissue in the digestive system.

The role of blood cells

The bone marrow is the soft, spongy material inside bones. It produces stem cells, which are unspecialised blood cells that usually grow into one of three main types of blood cells: red blood cells, white blood cells and platelets. Each type of blood cell has a specific function.

There are different types of white blood cells. The lymph nodes, lymph tissue and lymph fluid all contain the white blood cells known as lymphocytes. When germs become trapped in the lymph nodes, the nodes become swollen, which is a sign that your body is fighting an infection. For example, the lymph nodes in your neck may swell when you have a sore throat. The swelling happens because the lymphocytes in the lymph nodes multiply to fight off the virus or bacteria that is causing the infection.

Diseases such as lymphoma or treatments such as chemotherapy can lower the number of blood cells in the body, and this can cause particular symptoms:

• Low levels of white blood cells can cause neutropenia, which makes you more likely to get infections.
• Low levels of red blood cells can cause anaemia, which may make you look pale and feel tired, breathless and dizzy.
• Low levels of platelets can cause thrombocytopenia, which means you bruise or bleed easily.

For more information about the role of blood cells and all types of blood cancers, you can visit the Leukaemia Foundation.

What types are there?

Classical Hodgkin lymphoma and nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL) are the two main types of Hodgkin lymphoma. They differ in how they look under the microscope, and how they grow and spread.

What causes Hodgkin lymphoma?

The causes of Hodgkin lymphoma are largely unknown, but the risk factors include:

Certain viruses – Infection with Epstein-Barr virus (glandular fever or infectious mononucleosis) or human immunodeficiency virus (HIV) increases the risk, but this explains only a small number of Hodgkin lymphoma cases. Most people with Epstein- Barr virus or HIV will not develop Hodgkin lymphoma.

Family history – Having a parent, brother or sister who has had Hodgkin lymphoma slightly increases a person’s risk of developing it. However, this family link is uncommon.

Weakened immune system – The risk is higher if your immune system has been weakened. This can happen if you have an autoimmune disease or if you need to take medicines that suppress the immune system after an organ transplant.

Many people with known risk factors don’t develop Hodgkin lymphoma, and most people who do get it have no known risk Hodgkin lymphoma is not contagious.

Who gets Hodgkin lymphoma?

Each year in Australia, about 647 people are diagnosed with Hodgkin lymphoma. Classical Hodgkin lymphoma most commonly develops in younger people aged 15–29 and older people aged over 70, but it can occur at any age. It is more common in men than women. The much rarer nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL) mostly affects children, or men in their 30s and 40s.

What is non-Hodgkin lymphoma?

There are two main types of lymphoma: Hodgkin lymphoma and non-Hodgkin lymphoma. Non-Hodgkin lymphoma is more common. The two types look different when the diseased cells are examined under a microscope. A type of lymphocyte called a Reed-Sternberg cell is seen in most cases of Hodgkin lymphoma, but it is not found in non-Hodgkin lymphoma. This information is only about Hodgkin lymphoma.

For more on non-Hodgkin lymphoma, call Cancer Council 13 11 20 or see Non-Hodgkin lymphoma.