Non-Hodgkin lymphoma is an uncommon cancer that develops in the lymphatic system, which is a network of vessels and glands spread throughout your body.

The lymphatic system is part of your immune system. Clear fluid called lymph flows through the lymphatic vessels and contains infection-fighting white blood cells known as lymphocytes.

In non-Hodgkin lymphoma, the affected lymphocytes start to multiply in an abnormal way and begin to collect in certain parts of the lymphatic system, such as the lymph nodes (glands). The affected lymphocytes lose their infection-fighting properties, making you more vulnerable to infection.

The most common symptom of non-Hodgkin lymphoma is a painless swelling in a lymph node, usually in the neck, armpit or groin. 

Read more about the symptoms of non-Hodgkin lymphoma. 

Who is affected

About 80% of all lymphomas diagnosed are non-Hodgkin lymphoma. In the UK, more than 12,000 cases are diagnosed each year.

Non-Hodgkin lymphoma can occur at any age, but your chances of developing the condition increase as you get older, with most cases diagnosed in people over 65. Slightly more men than women are affected.

What causes non-Hodgkin lymphoma?

The exact cause of non-Hodgkin lymphoma is unknown.

However, your risk of developing the condition is increased if you have a medical condition that weakens your immune system, you take immunosuppressant medication or you have previously been exposed to a common virus called the Epstein-Barr virus (which causes glandular fever).

You may also have a slightly increased risk of developing non-Hodgkin lymphoma if a first-degree relative (such as a parent or sibling) has had the condition.

Read more about the causes of non-Hodgkin lymphoma.

How non-Hodgkin lymphoma is diagnosed

The only way to confirm a diagnosis of non-Hodgkin lymphoma is by carrying out a biopsy.

This is a minor surgical procedure where a sample of affected lymph node tissue is removed and studied in a laboratory.

Read more about diagnosing non-Hodgkin lymphoma.

Treatment and outlook

There are many subtypes of non-Hodgkin lymphoma, but they can generally be put into one of two broad categories:

• high-grade or aggressive non-Hodgkin lymphoma is where the cancer develops quickly and aggressively
• low-grade or indolent non-Hodgkin lymphoma is where the cancer develops slowly, and you may not experience any symptoms for many years

The outlook for non-Hodgkin lymphoma varies greatly depending on the exact type, grade and extent of the lymphoma, and the person’s age.

Low-grade tumours do not necessarily require immediate medical treatment, but are harder to completely cure. High-grade lymphomas need to be treated straightaway but tend to respond much better to treatment and can often be cured. 

The main treatments used for non-Hodgkin lymphoma are chemotherapy, radiotherapy and a type of targeted treatment called monoclonal antibody therapy.

Overall, most cases of non-Hodgkin lymphoma are considered very treatable. More than half of those with high grade disease are cured and about half of those with low grade disease will live at least 10 years.

However, there is a risk of long-term problems after treatment, including infertility and an increased risk of developing another type of cancer in the future.

Read more about treating non-Hodgkin lymphoma and complications of non-Hodgkin lymphoma.