What is Hodgkin lymphoma?
Hodgkin lymphoma is a blood cancer that begins in the white blood cells called lymphocytes. It is sometimes called Hodgkin disease. The name Hodgkin comes from the doctor who first described this cancer.
Hodgkin lymphoma 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 can appear 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:
- The lymphatic system
- What is lymphoma?
- Types of Hodgkin lymphoma
- What causes Hodgkin lymphoma?
- Who gets Hodgkin lymphoma?
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 consists of:
Lymph vessels – These thin tubes form a network 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 removing bacteria and cell debris, before being emptied into the bloodstream.
Lymph nodes (glands) – These small, bean-shaped structures are found along the lymph vessels. Lymph nodes are located in groups throughout the body, including the neck, underarms, chest, abdomen and groin. The lymph nodes filter the lymph fluid as it passes through the body, removing and destroying bacteria, viruses and other harmful substances.
Lymph tissue – This includes the lymph nodes, spleen, bone marrow, thymus, tonsils, and some tissues in the digestive tract.
The lymph nodes, lymph tissue and lymph fluid all contain white blood cells called lymphocytes, which help fight infection. When germs become trapped in the lymph nodes, they become swollen, which is a sign that your body is fighting an infection. For example, the glands 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.
The lymphatic organs include:
Thymus gland – This is found inside the rib cage, behind the breastbone. The thymus gland helps produce white blood cells.
Bone marrow – This is the soft, spongy material inside bones. Bone marrow produces three types of blood cells: oxygen-carrying red blood cells; infection-fighting white blood cells, including lymphocytes; and platelets, which help the blood to clot.
Spleen – The spleen is found on the left side of the abdomen, under the ribs. It stores lymphocytes, filters waste products from the blood, and destroys old blood cells, abnormal cells and bacteria.
Tonsils – The tonsils are two small collections of lymphatic tissue at the back of the throat that trap inhaled or ingested germs.
What is lymphoma?
Lymphoma is a term used to describe cancers of the lymphatic system. Lymphomas begin in the white blood cells called lymphocytes. When lymphocytes become damaged, they grow and multiply uncontrollably, causing enlarged lymph nodes.
If these abnormal cells continue to build up, they can spread and form a tumour in any part of the lymphatic system. As the damaged lymphocytes replace normal cells, the body’s immune system often becomes less able to resist and fight infections.
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 usually seen in Hodgkin lymphoma, but it is not found in non-Hodgkin lymphoma.
Sometimes other types of cancer spread (metastasise) to the lymph nodes. This is not lymphoma. For example, breast cancer that has spread to the lymph nodes is called secondary or metastastic breast cancer.
Types of Hodgkin lymphoma
There are two different types of Hodgkin lymphoma: classical Hodgkin lymphoma and nodular lymphocyte-predominant Hodgkin lymphoma. These two types differ in how they look under the microscope, and how they grow and spread.
About 95% of all cases of Hodgkin lymphoma are classical Hodgkin lymphoma. The cells of this type of Hodgkin lymphoma are called Reed-Sternberg cells.
There are four subtypes of classical Hodgkin lymphoma. Each one looks different under a microscope, grows in its own way and involves different sites of the body. They are:
- nodular sclerosis – the most common subtype; affects 60–80% of people with Hodgkin lymphoma
- mixed cellularity – affects 25–30% of people with Hodgkin lymphoma and is usually more advanced at diagnosis
- lymphocyte-rich – affects 5% of people with Hodgkin lymphoma
- lymphocyte-depleted – affects fewer than 5% of people with Hodgkin lymphoma.
NLPHL occurs in fewer than 5% of people with Hodgkin lymphoma. It mostly affects children or men in their 30s and 40s. The main symptom is enlarged lymph nodes in the neck, chest, armpit or groin.
NLPHL is usually diagnosed via excision biopsy. The cells in NLPHL differ from classical Hodgkin lymphoma. They are known as “popcorn cells” because of how they look under a microscope.
The management of NLPHL is different from classical Hodgkin lymphoma. Sometimes, the only treatment for NLPHL is an operation to remove the lymph nodes, followed by regular check-ups to make sure the cancer hasn’t returned. This is called “watch and wait”.
What causes Hodgkin lymphoma?
The causes of Hodgkin lymphoma are largely unknown. Researchers think a combination of factors relating to a person’s genes and their environment may cause Hodgkin lymphoma. Risk factors include:
Epstein-Barr virus and HIV – People who have a history of Epstein-Barr virus infection (also called glandular fever or infectious mononucleosis) or human immunodeficiency virus (HIV) have a higher chance of developing classical Hodgkin lymphoma. However, this accounts for only a small proportion of people who have 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, as most people with Hodgkin lymphoma do not have a family history.
Weakened immune system – This could be caused by an autoimmune disease, having undergone immune suppression or taking certain medicines 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 factors. Hodgkin lymphoma is not contagious.
Who gets Hodgkin lymphoma?
Hodgkin lymphoma is a rare form of cancer – it makes up only about 0.5% of all cancers diagnosed in Australia.
About 11% of all lymphomas diagnosed are types of Hodgkin lymphoma. The rest are non-Hodgkin lymphomas.
Each year in NSW, about 200 people are diagnosed with Hodgkin lymphoma. It most commonly develops in younger people aged 15–29 and older people aged over 65, but it can occur at any age. It is more common in men than women.