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A risk factor is anything that might increase a person’s chances of getting cancer. Different cancers have different risk factors.

Lifestyle-related risk factors such as body weight, physical activity, diet, and the use of tobacco or alcohol play a major role in many adult cancers. But these factors usually take many years to influence cancer risk, and they are not thought to have much of an effect on the risk of childhood cancers, including non-Hodgkin lymphoma (NHL).

Researchers have found some factors that can increase a child’s risk of NHL. But most children with NHL do not have any known risk factors that can be changed.

Age, sex, and race

Non-Hodgkin lymphoma is rare in children in general, but it is more common in older children than in younger ones. It is also more common in boys than in girls and in White children than in Black children. The reasons for these differences are not clear.

Having a weakened immune system

Some types of immune system problems have been linked with a higher risk of NHL in children and teens.

Congenital (present at birth) immune deficiency syndromes

Some children are born with an abnormal immune system because of a genetic (inherited) syndrome. Along with an increased risk of serious infections, these children also have a higher risk of developing NHL (and sometimes other cancers as well). These syndromes include:

• Wiskott-Aldrich syndrome
• Nijmegen syndrome
• Ataxia-telangiectasia
• Common variable immunodeficiency
• X-linked lymphoproliferative syndrome

Organ transplants

Children who have had organ transplants are treated with drugs that weaken their immune system to prevent it from attacking the new organ. These children have an increased risk of developing NHL that is almost always caused by Epstein-Barr virus infection (see below). The risk depends on which drugs and what doses are used.

Human immunodeficiency virus (HIV) infection and AIDS

Infection with HIV, the virus that causes AIDS, can weaken the immune system. Children with HIV generally get the infection from contact with their mother's blood, usually before or during birth. Because HIV infection is a risk factor for developing NHL, doctors may recommend that children with NHL be tested for HIV infection.

Epstein-Barr virus infection

In areas of Africa where Burkitt lymphoma is common, chronic infection with both malaria and the Epstein-Barr virus (EBV) is an important risk factor. EBV has been linked with almost all Burkitt lymphomas in Africa. In the United States, EBV has been linked with about 15% of Burkitt lymphomas. It is also linked to most lymphomas that occur after an organ transplant.

EBV infection is life-long, although it doesn't cause serious problems in most people. In 蜜桃传媒s who are first infected with EBV as teens or young adults, it can cause infectious mononucleosis, sometimes known simply as mono. Most 蜜桃传媒s have been infected with EBV by the time they are adults, but the infection seems to occur later in life in the United States than in Africa, which may help explain why it is less likely to cause childhood lymphoma here.

Exactly how EBV is linked to NHL is not completely understood, but it seems to have to do with the ability of the virus to infect and alter B lymphocytes. (For more information, see What Causes Non-Hodgkin Lymphoma in Children?)

Radiation exposure

Radiation exposure may be a minor risk factor in childhood NHL.

Survivors of atomic bomb exposures and nuclear reactor accidents have an increased risk of developing some types of cancer. Leukemia and thyroid cancers are the most common, but there is a slightly increased risk of NHL as well.

Patients treated with radiation therapy for other cancers have a slightly increased risk of NHL later in life. But it usually takes many years for this to develop, so these secondary cases of NHL are more common in adults than in children.

The possible risks from fetal or childhood exposure to lower levels of radiation, such as from x-ray tests or CT scans, are not known for sure. If there is an increase in risk for NHL or other cancers it is likely to be small, but to be safe, most doctors recommend that pregnant women and children not get these tests unless they are absolutely needed.

Other possible risk factors

Some research has suggested that a family history of NHL (in a brother, sister, or parent) might raise the risk of lymphoma. Lymphoma risk may also be higher in children of older mothers. More research is needed to confirm these findings, but if there is an increased risk tied to these factors, it is likely to be small.