Non-Hodgkin lymphoma

Cancer is a disease of the cells, which are the body’s basic building blocks. Our bodies constantly make new cells to help us grow, replace worn-out tissue and heal damaged cells after an injury. Normally, cells grow, multiply and die in an orderly way.

Sometimes cells don’t grow, divide and die in the usual way. This may cause different kinds of cancer. Most cancers, such as breast or bowel cancer, are solid cancers. In these, the abnormal cells form a lump called a tumour.

Other cancers that affect the blood, bone marrow and lymphatic system are know as blood cancers. There are three main groups of blood cancers: leukaemia, lymphoma and myeloma.

The blood is made up of different types of blood cells. Blood cells are made in the bone marrow – a spongy material in the middle of our bones. The main types of blood cells are red blood cells, white blood cells and platelets. Each of these cell types has a different function in the body.

Blood cancers develop when blood cells aren’t made properly. In most blood cancers, an abnormal type of blood cell grows out of control and upsets normal cell production.

This can reduce the bone marrow’s ability to produce normal levels of other blood cells, which affects the way that the rest of the body works. Meanwhile, the abnormal cells spill out into the bloodstream or the lymphatic system. Without treatment, many of the body’s key functions will be increasingly affected.

Lymphoma is a term used to describe cancers that develop in the lymphatic system. Lymphomas begin in a type of white blood cell called lymphocytes. When lymphocytes become malignant, they grow and multiply uncontrollably, commonly causing enlarged lymph nodes.

If these abnormal cells continue to build up, they can spread to any part of the lymphatic system. As the damaged lymphocytes multiply and replace normal cells, the body’s immune system becomes less able to fight infections.

Sometimes other types of cancer spread to the lymph nodes. This is not lymphoma. For example, breast cancer that has spread to the lymph nodes is called secondary or metastatic breast cancer.

Non-Hodgkin lymphoma is a cancer that starts in the lymphatic system. The lymphatic system is a key part of the immune system, which helps protect the body against disease and infection.

It consists of:

Lymph vessels – These thin tubes form a large network throughout the body. Lymph vessels carry lymph fluid around the body.

Lymph fluid – This clear fluid travels from the tissues in the body, through the lymph vessels, before being emptied into the bloodstream. It carries nutrients, antibodies and immune cells.

Lymph nodes (glands) – These small, bean-shaped structures are found along the lymph vessels. Lymph nodes are located throughout the body, including the neck, underarms, chest, abdomen and groin. Lymphocytes in the lymph nodes clean the lymph fluid as it passes through the body, helping to remove and destroy bacteria, viruses and other harmful substances.

When germs become trapped in the lymph nodes, the lymph nodes swell, which is a sign that lymphocytes have multiplied to fight off the germs. For example, the glands in your neck may swell when you have a sore throat.

Lymph tissue – This is found throughout the body, e.g. in the lymph nodes, spleen, bone marrow, thymus and tonsils.

Lymphocytes – Lymph fluid, lymph nodes and lymph tissue all contain white blood cells called lymphocytes, which help protect the body against disease and infection. The three main types of lymphocytes – B-cells, T-cells and NK-cells – are produced in the bone marrow. Non-Hodgkin lymphoma starts in these blood cells.

Anatomy of the lymphatic system

The lymphatic organs include:

Bone marrow – This is the soft, spongy material inside bones. Bone marrow produces three types of blood cells: red blood cells; white blood cells (including some types of lymphocytes); and platelets. In non‑Hodgkin lymphoma, abnormal cells multiply and crowd the bone marrow, reducing its ability to make normal blood cells.

Thymus gland – This is found inside the rib cage, behind the breastbone. The thymus gland helps produce lymphocytes.

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 cells, abnormal cells and bacteria.

Tonsils – The tonsils are two small collections of lymphatic tissue at the back of the throat. They trap inhaled or ingested germs.

There are many different types of non-Hodgkin lymphoma. It is classified according to whether the cancer started in B-cell, T-cell or NK-cell lymphocytes.

Below we describe some of the more commonly diagnosed types of non-Hodgkin lymphoma. NK‑cell lymphomas are very rare.

Non-Hodgkin lymphoma can also be classified by how fast it is growing.

Common types of non-Hodgkin lymphoma:

B-cell lymphomas (around 85% of cases)

• diffuse large B-cell — a fast-growing cancer that often starts in lymph nodes; the most common type of non-Hodgkin lymphoma in Australia; an intermediate-grade lymphoma.
• follicular — cancer cells grow slowly in lymph nodes in circular groups called follicles; may be low or intermediate-grade.
• small lymphocytic — a slow-growing cancer that is similar to chronic lymphocytic leukaemia; a low‑grade lymphoma.
• mantle cell — develops in the outer edge (mantle zone) of B-cells in the lymph nodes; although a low-grade lymphoma, it often acts like a high-grade lymphoma and grows quickly.

T-cell lymphomas (around 15% of cases)

• precursor T-lymphoblastic — starts in immature (precursor) T-cells in the lymph nodes and the spleen; a high-grade lymphoma.
• peripheral T-cell — often occurs as widespread enlarged, painless lymph nodes; an intermediate or high-grade lymphoma.
• cutaneous T-cell — primarily affects the skin and starts as red, scaly patches or raised bumps that can be itchy; a low-grade lymphoma.

In most cases of non-Hodgkin lymphoma, the cause is unknown. However, there are some factors that may increase the risk of a person developing non-Hodgkin lymphoma:

Weakened immune system – The immune system is weakened in people with HIV and people taking medicines called immunosuppressants. These include drugs to treat HIV and drugs that are given to people after an organ transplant. People with autoimmune diseases, such as rheumatoid arthritis and coeliac disease, also have a weakened immune system.

Infections – Some infections can slightly increase the risk of non-Hodgkin lymphoma. These include Helicobacter pylori, HTLV-1 (human T-lymphotropic virus 1), hepatitis C, Epstein-Barr virus and human herpesvirus 8.

Family history – Having a parent, brother or sister who has had non-Hodgkin lymphoma slightly increases a person’s risk of developing it. However, this family link is rare and most people with non-Hodgkin lymphoma do not have a family history.

Each year in NSW, about 1700 people are diagnosed with non-Hodgkin lymphoma. It is more common in men than women. Most cases occur in adults aged 60 and older. However, non-Hodgkin lymphoma can also occur in young adults and children.