Risks and causes of non-Hodgkin lymphoma
We don’t know what causes most cases of non-Hodgkin lymphoma (NHL). But there are some risks factors that can increase your risk of developing it. These include certain types of infection or a weakened 
.
Anything that can increase your risk of getting a disease is called a risk factor.
Different cancers have different risk factors. Having one or more of these risk factors doesn't mean you will definitely get that cancer.
Age
Although NHL can happen at any age, more than 35 out of 100 (more than 35%) of people diagnosed with NHL are aged 75 and over.
Weakened immune system
People whose is not working as well as it should are more likely to develop a lymphoma. Immunity can be lowered for the following reasons:
- taking drugs to stop organ rejection after a transplant
- being born with a rare medical condition that affects immunity
autoimmune diseases and their treatment
If you have autoimmune disease, your own immune system attacks your body tissue as it would attack a germ. Some autoimmune diseases can increase your risk of developing certain types of lymphoma. These autoimmune diseases include:
- rheumatoid arthritis
- haemolytic anaemia
- coeliac disease
- Sjogren's syndrome
- systemic lupus erythematosus
Infections
Some infections can increase your risk of developing NHL. But most of these infections are uncommon in the UK. So in the UK, the actual number of cases caused by infections is small.
The infection is only part of a complex process for cancer to develop. Most people with these infections don't go on to develop NHL.
NHL is not infectious. You can't pass it on to someone else or catch it.
Helicobacter pylori
Helicobacter pylori is a bacterial infection. It can cause a rare type of lymphoma that starts in the stomach. This type of lymphoma is called MALT lymphoma. MALT stands for mucosa associated lymphoid tissue. It starts in lymphatic tissue in the lining of the stomach.
Human immunodeficiency virus (HIV)
Human immunodeficiency virus (HIV) increases your risk of developing NHL. This risk is greater for some types of NHL, such as diffuse large B cell lymphoma (DLBCL).
Doctors can successfully treat HIV with highly active antiretroviral therapy (HAART). The risk of NHL in people with HIV has decreased since the introduction of HAART in 1996.
T cell lymphoma virus 1 (HTLV1)
Human T cell lymphoma virus 1 (HTLV1) is a rare virus in the UK. It is more common in Japan, Africa and the Caribbean. Infection with HYLV1 can increase your risk of developing a rare lymphoma. This type is called adult T-cell leukaemia / lymphoma.
Epstein Barr virus
The Epstein Barr virus increases your risk of developing a type of NHL called Burkitt lymphoma. Epstein Barr is is the virus that causes glandular fever (mononucleosis). People who've had mononucleosis might have a higher risk of developing NHL. But most people who have had mononucleosis never get lymphoma.
Burkitt lymphoma is more common in Africa than Europe.
Hepatitis
People with the hepatitis C virus have an increased risk of developing NHL. But this is a small increased risk for people living in this country. The hepatitis B virus might also increase the risk but the evidence is less clear.
Coeliac disease
This is a disease of the small bowel. It affects about 1 in every 100 people. People with coeliac disease have an abnormal immune reaction to gluten, a protein found in rye, wheat and barley. This reaction causes inflammation of the small bowel.
Coeliac disease is a risk factor for a rare type of lymphoma of the small bowel. This is called enteropathy-associated T-cell lymphoma (EATL).
The risk seems to be higher in people with poorly managed coeliac disease. If you have coeliac disease, sticking to a gluten free diet might help reduce your risk.
Family history of NHL
Having a close relative diagnosed with NHL slightly increases your risk of getting NHL. A close relative means a parent, brother or sister. But this is not a major risk factor. The general risk is still small. Most people who get NHL don't have a relative who has had it.
Previous cancer and treatment
There might be a link between some other types of cancer and an increased risk of NHL. These include:
- blood cancers such as Hodgkin lymphoma and leukaemia
- melanoma
- prostate cancer
Doctors are unsure whether this increase in risk is because of the effect of treatment for the first cancer. Or because NHL shares some of the same risk factors that caused the first cancer.
But the increase in risk of developing are very small compared to the risk of not having the treatment for the original cancer.
Breast Implant Associated Anaplastic Large Cell Lymphoma (BIA-ALCL)
Some women who have a breast implant can develop a rare type of lymphoma of the breast. This is called anaplastic large cell lymphoma (ALCL). This includes women who have had:
- a breast enlargement
- an implant to reconstruct their breast following breast cancer surgery
The risk of a woman developing ALCL following an implant is very small. This can happen some years later. On balance, doctors believe that implants are a safe option for breast reconstruction. But women should be made aware of this risk. This link is associated with textured implants. There have been no women diagnosed with this following a smooth implant.
Those who have had a breast implant should contact their doctor if they have a lump of swelling in that breast. This type of lymphoma is usually easy to treat with surgical removal of the lymphoma and the implant.
Other possible causes
Stories about potential causes are often in the media. It isn’t always clear which of the ideas reported are supported by good evidence.
You might have heard about a possible cause which we haven’t included here. This is either because there is no evidence to support it, or because it is not fully clear what the evidence shows.
